Adhesive sheet

ABSTRACT

Provided is a pressure sensitive adhesive sheet containing a resin layer on a substrate or a release material, at least a surface (α) of the resin layer being opposite to the side thereof on which the substrate or the release material is provided having pressure sensitive adhesiveness, wherein one or more concave portions formed not by transferring an emboss pattern exist on the surface (α). The pressure sensitive adhesive sheet has excellent air escape property capable of readily removing air accumulation that may be formed on attaching

TECHNICAL FIELD

The present invention relates to a pressure sensitive adhesive sheet.

BACKGROUND ART

A general pressure sensitive adhesive sheet is constituted by a substrate, a pressure sensitive adhesive layer formed on the substrate, and a release material provided on the pressure sensitive adhesive layer depending on necessity, and in use, after removing the release material in the case where the release material is provided, the general pressure sensitive adhesive sheet is attached to an adherend by making the pressure sensitive adhesive layer into contact therewith.

A pressure sensitive adhesive sheet having a large attaching area, which may be used for identification or decoration, masking for painting, surface protection of a metal plate or the like, and the like, has a problem that on attaching the sheet to an adherend, air accumulation is liable to occur between the pressure sensitive adhesive layer and the adherend, and the portion with the air accumulation is recognized as “blister”, so as to prevent the pressure sensitive adhesive sheet from being attached cleanly to the adherend.

For solving the problem, for example, PTL 1 describes a pressure sensitive adhesive sheet having grooves with a particular shape that are disposed artificially in a prescribed pattern on the surface of the pressure sensitive adhesive layer by making a release material having a fine emboss pattern into contact with the surface of the pressure sensitive adhesive layer.

There is described that, by using the pressure sensitive adhesive sheet, it is possible to escape the “air accumulation” formed on attaching to an adherend, to the exterior through the grooves formed artificially on the surface of the pressure sensitive adhesive layer.

CITATION LIST Patent Literature

PTL 1: JP 2001-507732 A

SUMMARY OF INVENTION Technical Problem

However, the pressure sensitive adhesive sheet having a pressure sensitive adhesive layer having grooves with a particular shape disposed in a prescribed pattern, as shown in PTL 1, has a problem that when the width of the grooves is small, it is difficult to vent the air, and when the width of the grooves is large, not only the surface of the substrate is dented to deteriorate the appearance, but also the pressure sensitive adhesive strength is lowered.

In the pressure sensitive adhesive sheet, the grooves disposed in a prescribed pattern deteriorate the pressure sensitive adhesive strength locally in the portion having the grooves disposed, and after attaching the pressure sensitive adhesive sheet to an adherend, there is a possibility that the sheet is detached therefrom in the portion.

In the case where the pressure sensitive adhesive sheet is attached to an adherend and then peeled again therefrom, there is a possibility of adhesive deposits remaining on the adherend depending on the peeling direction of the pressure sensitive adhesive sheet since the pressure sensitive adhesion characteristics of the pressure sensitive adhesive sheet varies locally. For example, in the case where the pressure sensitive adhesive sheet having the pressure sensitive adhesive layer wherein the grooves of a lattice pattern is disposed is peeled obliquely, there is a possibility of adhesive deposits remaining on the adherend.

Furthermore, in the case where the pressure sensitive adhesive sheet is punched out, there is a possibility that the disposition pattern of the grooves overlaps the punching pattern. In this case, the cutting depth may fluctuate to provide a problem that a cut line cannot be suitably formed in the pressure sensitive adhesive sheet.

In general, such a process of forming a trigger for peeling in order to facilitate the peeling of the release material (i.e., a so-called back slit) by only cutting a release material provided on the pressure sensitive adhesive sheet step may be performed. In the case where the above step is performed, it is the general procedure that the release material is once peeled off from the pressure sensitive adhesive sheet, and after putting notches in the release material, the release material and the pressure sensitive adhesive layer of the pressure sensitive adhesive sheet are again laminated with each other.

In the pressure sensitive adhesive sheet described in PTL 1, however, due to the use of an embossed liner as the release material, it is necessary to provide a separate release material that is not embossed. Because, it is difficult to follow to the emboss pattern of the release material on laminating again the release material and the pressure sensitive adhesive layer.

In PTL 1, further, for forming a minute structure in the pressure sensitive adhesive layer, such a method is used that the pressure sensitive adhesive layer is once formed by coating a pressure sensitive adhesive on the embossed liner, and then the pressure sensitive adhesive layer and a substrate are laminated (i.e., a so-called transfer coating method). However, in the case where a substrate having a surface with low polarity, such as a polyolefin substrate, is used, sufficient adhesiveness cannot be obtained between the substrate and the pressure sensitive adhesive layer by the method.

Moreover, as different from a release material formed of paper, a release material formed of a resin film is difficult to form a fine emboss pattern to a pressure sensitive adhesive layer.

In addition, the pressure sensitive adhesive sheet described in PTL 1 is inferior in blister resistance, and thus has a problem that blister is liable to occur in the case where the sheet is used at a high temperature.

An object of the present invention is to provide a pressure sensitive adhesive sheet that has an excellent air escape property capable of easily removing air accumulation that may be formed on attaching to an adherend, and is excellent in blister resistance and pressure sensitive adhesion characteristics.

Solution to Problem

The present inventors have found that a pressure sensitive adhesive sheet having a resin layer on a substrate or a release material and having, on the surface of the resin layer opposite to the side thereof on which the substrate or the release material is provided, one or more concave portions formed not by transferring an emboss pattern can solve the above-mentioned problems, and have completed the present invention.

Specifically, the present invention provides the following [1] to [15].

[1] A pressure sensitive adhesive sheet having a resin layer on a substrate or a release material, at least a surface (α) of the resin layer being opposite to the side thereof on which the substrate or the release material is provided having pressure sensitive adhesiveness,

wherein one or more concave portions formed not by transferring an emboss pattern exist on the surface (α).

[2] The pressure sensitive adhesive sheet according to [1], wherein the shapes of the one or more concave portions have irregular shapes. [3] The pressure sensitive adhesive sheet according to [1] or [2], wherein the one or more concave portions are formed through self-formation of the resin layer. [4] The pressure sensitive adhesive sheet according to any one of [1] to [3], wherein the plural concave portions exist on the surface (α). [5] The pressure sensitive adhesive sheet according to [4], wherein the positions of the plural concave portions have no periodicity. [6] The pressure sensitive adhesive sheet according to [4] or [5], wherein the one or more concave portions exist irregularly on the surface (α). [7] The pressure sensitive adhesive sheet according to any one of [1] to [6], wherein the shapes of one or more attached faces on the surface (α) of the resin layer have irregular shapes. [8] The pressure sensitive adhesive sheet according to [7], wherein the plural attached faces exist. [9] The pressure sensitive adhesive sheet according to any one of [1] to [8], wherein the resin layer contains a resin part (X) containing a resin as a main component and a particle part (Y) consisting of fine particles. [10] The pressure sensitive adhesive sheet according to any one of [1] to [9], wherein the resin layer is formed of a multilayer structure having a fine particles-containing layer that contains fine particles. [11] The pressure sensitive adhesive sheet according to any one of [1] to [10], wherein the resin layer has a multilayer structure of, as laminated in this order from the side on which the substrate or the release material is provided, a layer (Xβ) mainly containing a resin part (X), a layer (Y1) containing a particle part (Y), and a layer (Xα) mainly containing a resin part (X). [12] The pressure sensitive adhesive sheet according to any one of [1] to [10], wherein the layer (Xβ) is a layer formed by a composition containing the resin as a main component, the layer (Y1) is a layer formed by a composition containing the fine particles, and the layer (Xα) is a layer formed by a composition containing the resin as a main component. [13] A viscoelastic layer having, on at least one surface thereof, one or more concave portions formed not by transferring an emboss pattern. [14] A method for producing a pressure sensitive adhesive sheet according to any one of [1] to [10], which includes at least the following steps (1) and (2): Step (1): a step of forming a coating film (x′) formed by a composition (x) containing the resin as a main component, and a coating film (y′) formed by a composition (y) containing the fine particles, Step (2): a step of drying the coating film (x′) and the coating film (y′) formed in the step (1) simultaneously. [15] A method for producing a pressure sensitive adhesive sheet according to [12], which includes at least the following steps (1A) and (2A): Step (1A): a step of forming, on a substrate or a release material, a coating film (xβ′) formed by the composition (xβ) containing the resin as a main component, a coating film (y′) formed by the composition (y) containing the fine particles and a coating film (xα′) formed by the composition (xα) containing the resin as a main component, by laminating in this order, Step (2A): a step of drying the coating film (xβ′), the coating film (y′) and the coating film (xα′) formed in the step (1A) simultaneously. [16] A method for producing a pressure sensitive adhesive sheet according to [12], which includes at least the following steps (1B) and (2B):

step (1B): a step of forming, on a layer (Xβ) mainly containing a resin part (X) that is provided on a substrate or a release material, a coating film (y′) formed by the composition (y) containing the fine particles and a coating film (xα′) formed by the composition (xα) containing the resin as a main component, by laminating in this order; and

step (2B): a step of drying the coating film (y′) and the coating film (xα′) formed in the step (1B) simultaneously.

Advantageous Effects of Invention

The pressure sensitive adhesive sheet of the present invention has excellent air escape property capable of readily removing air accumulation that may be formed on attaching to an adherend, and has good pressure sensitive adhesion characteristics.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross sectional view showing an example of the structure of the pressure sensitive adhesive sheet of the present invention.

FIG. 2 is a schematic cross sectional view showing an example of the shape of the resin layer on the side of the surface (α) of the pressure sensitive adhesive sheet of the present invention.

FIG. 3 is a schematic plan view showing an example of the surface (α) of the resin layer of the pressure sensitive adhesive sheet of the present invention.

FIG. 4 is images of the pressure sensitive adhesive sheet produced in Example 1, taken through a scanning electron microscope; and (a) of FIG. 4 is an image of a cross section of the pressure sensitive adhesive sheet, and (b) of FIG. 4 is a perspective image in observation of the side of the surface (α) of the resin layer of the pressure sensitive adhesive sheet.

FIG. 5 is images obtained by observing the pressure sensitive adhesive sheet produced in Example 10 with a scanning electron microscope, in which (a) of FIG. 5 is an image of a cross section of the pressure sensitive adhesive sheet, and (b) of FIG. 5 is a perspective image in observation on the side of the surface (α) of the resin layer of the pressure sensitive adhesive sheet.

FIG. 6 is images obtained by observing the pressure sensitive adhesive sheet produced in Comparative Example 1 with a scanning electron microscope, in which (a) of FIG. 6 is a cross sectional image of the pressure sensitive adhesive sheet, and (b) of FIG. 6 is a perspective image in observation on the side of the surface (α) of the resin layer of the pressure sensitive adhesive sheet.

FIG. 7 is a binary image obtained in such a manner that the surface (α) of the resin layer of the pressure sensitive adhesive sheet produced in Example 1 is attached to a smooth surface of a light transmissive adherend, a digital image is obtained by observing the surface (α) from the side of the light transmissive adherend, and a region surrounded by a square having an edge length of 2 mm that is arbitrarily selected on the digital image is subjected to an image processing (binary processing).

FIG. 8 is a binary image obtained in such a manner that the surface (α) of the resin layer of the pressure sensitive adhesive sheet produced in Example 10 is attached to a smooth surface of a light transmissive adherend, a digital image is obtained by observing the surface (α) from the side of the light transmissive adherend, and a region surrounded by a square having an edge length of 2 mm that is arbitrarily selected on the digital image is subjected to an image processing (binary processing).

FIG. 9 is a binary image obtained in such a manner that the surface (α) of the resin layer of the pressure sensitive adhesive sheet produced in Comparative Example 1 is attached to a smooth surface of a light transmissive adherend, a digital image is obtained by observing the surface (α) from the side of the light transmissive adherend, and a region surrounded by a square having an edge length of 2 mm that is arbitrarily selected on the digital image is subjected to an image processing (binary processing).

DESCRIPTION OF EMBODIMENTS

In the present invention, for example, an expression “YY containing a component XX as a main component” or an expression “YY mainly containing a component XX” means that “among the components contained in YY, a component having a largest content is the component XX”. A concrete content of the component XX in this expression is generally 50% by mass or more, and is preferably 65 to 100% by mass, more preferably 75 to 100% by mass, even more preferably 85 to 100% by mass, relative to the total amount (100% by mass) of YY.

In the present invention, for example, “(meth)acrylic acid” indicates both “acrylic acid” and “methacrylic acid”, and the same shall apply to other similarity terms.

Regarding a preferred numerical range (for example, a range of content or the like), a lower limit and an upper limit that are expressed in stages can be combined each independently. For example, from an expression of “preferably 10 to 90, more preferably 30 to 60”, “the preferred lower limit (10)” and “the preferred upper limit (60)” may be combined to be “10 to 60”.

[Configuration of Pressure Sensitive Adhesive Sheet]

First, the constitution of the pressure sensitive adhesive sheet of the present invention is described.

The pressure sensitive adhesive sheet of the present invention has, on a substrate or a release material, a resin layer.

FIG. 1 is a schematic cross sectional view showing an example of the structure of the pressure sensitive adhesive sheet of the present invention.

As specific structures of a pressure sensitive adhesive sheet that are embodiments of the present invention, for example, there are mentioned a pressure sensitive adhesive sheet 1 a having a resin layer 12 on a substrate 11 as shown by FIG. 1(a), and a pressure sensitive adhesive sheet 1 b having a resin layer 12 on a release material 14 as shown by FIG. 1(b).

In the pressure sensitive adhesive sheet of the present invention, at least a surface (α) 12 a of the resin layer 12 on the side opposite to the side on which the substrate 11 or the release material 14 is provided (hereinafter this may be simply referred to as “surface (α)”) has pressure sensitive adhesiveness.

Accordingly, from the viewpoint of handleability, the pressure sensitive adhesive sheet of the embodiment of the present invention preferably has a configuration of a pressure sensitive adhesive sheet 2 a or 2 b as shown by FIG. 1 (c) or FIG. 1 (d), where a release material 14 a is further arranged on the surface (α) 12 a of the resin layer 12 in the pressure sensitive adhesive sheet 1 a or 1 b shown in FIG. 1.

In the pressure sensitive adhesive sheet of the embodiment of the present invention, the surface (β) 12 b of the resin layer 12 on the side which the substrate 11 or the release material 14 is provided (hereinafter this may be simply referred to as “surface (β)”) may also have pressure sensitive adhesiveness. When the surface (β) also has pressure sensitive adhesiveness, in the pressure sensitive adhesive sheet 1 a or 2 a shown by FIG. 1 (a) or FIG. 1 (c), the adhesion between the resin layer 12 and the substrate 11 can be good, and the pressure sensitive adhesive sheet 1 b or 2 b shown by FIG. 1 (b) or FIG. 1 (d) may be a double-sided pressure sensitive adhesive sheet.

The resin layer 12 that the pressure sensitive adhesive sheet of the present invention has preferably contains a resin part (X) containing a resin as a main component and a particle part (Y) consisting of fine particles.

Since the resin layer contains the particle part (Y), the resultant pressure sensitive adhesive sheet can effectively prevent formation of blisters when used at high temperatures.

In addition, the concave portions 13 existing on the surface (α) also play a role of air-discharge channels for removing outside the “air accumulation” to be formed in adhering the surface (α) of the resin layer of the pressure sensitive adhesive sheet of the present invention to an adherend.

The length of the concave portion 13 in a planar view of the concave portion 13 existing on the surface (α) is not specifically limited. Namely, the concave portion 13 includes relatively long groove-like one and a relatively short pit-like one.

Regarding the distribution pattern of the resin part (X) and the particle part (Y) in the resin layer 12, the resin parts (X) and the particle parts (Y) may be distributed almost evenly as one pattern, or as a different pattern, an area mainly containing the resin parts (X) and an area mainly containing the particle parts (Y) may be locally divided.

In addition, as shown by FIG. 1 (a) to FIG. 1 (d), in the area where the concave portions 13 exist on the surface (α) of the resin layer 12, the pattern may be such that the proportion of the particle parts (Y) is smaller than in the other areas, or the particle parts (Y) may not be partly present.

As described above, the one or more concave portions on the surface (at) of the resin layer that the pressure sensitive adhesive sheet of the present invention has differ from grooves that have pre-designed shapes, such as those formed through embossed pattern transfer, for example, those formed by pressing an embossed release material onto the surface of the resin layer.

Preferably, the one or more concave portions are formed through self-formation of the resin layer.

In the present invention, “self-formation” means a phenomenon of naturally forming a disorganized profile in a process of self-sustaining formation of a resin layer, and more precisely, means a phenomenon of naturally forming a disorganized profile in a process of self-sustaining formation of a resin layer by drying a coating film formed of a composition that is a forming material for a resin layer.

Namely, the one or more concave portions formed through self-formation of the resin layer are ones formed in the step of drying the coating film formed of the composition that is a forming material for the resin layer.

The shapes of the one or more concave portions thus formed through self-formation of the resin layer in the manner as above may be controlled in some degree by controlling the drying condition or the kind and the content of the component in the composition that is a forming material for the resin layer, but differ from grooves to be formed through embossed pattern transfer, and it may be said that “it is substantially impossible to reproduce exactly the same shapes”.

In addition, the one or more concave portions are not those to be formed at previously determined positions, like grooves to be formed through embossed pattern transfer using a release material having an embossed pattern or the like.

The one or more concave portions are not those formed in predetermined positions, like grooves to be formed through embossed pattern transfer using an embossed pattern-having release material or the like.

Namely, the one or more concave portions are not those formed through embossed pattern transfer but have irregular shapes, and are formed through self-formation not having periodicity.

Preferably, the one or more concave portions existing on the surface (α) of the resin layer that the pressure sensitive adhesive sheet of the present invention has do not have a predetermined pattern. Here, “predetermined pattern” is meant to indicate, when attention is paid to the shape of one concave portion, a shape of a predetermined recurring unit that the concave portions have.

From the viewpoint of providing a pressure sensitive adhesive sheet having improved air escape property, it is preferable that the concave portions existing on the surface (α) of the resin layer that the pressure sensitive adhesive sheet of the present invention has can be visually recognized from the side of the surface (α) of the exposed resin layer by observing with naked eyes.

Further, as shown in FIG. 1(a), preferably, a plurality of such concave portions exist not having any periodicity, and also preferably, the concave portions exist irregularly on the surface (α).

Here, the wording “the shapes have irregular shapes” means that in a planar view or a stereoscopic view of the shapes of the one or more concave portions, the shapes thereof do not have any specific shape such as a shape surrounded by a circle or a line alone (circle, triangle, square, etc.) and the shapes thereof do not have any regularity, and the individual concave portions do not have any similarity with each other.

The “self-formation” means a phenomenon of naturally forming a disorganized profile in a process of self-sustaining formation of a resin layer, and more precisely, means a phenomenon of naturally forming a disorganized profile in a process of self-sustaining formation of a resin layer by drying a coating film formed of a composition that is a forming material for a resin layer.

The shapes of the one or more concave portions thus formed through self-formation of the resin layer in the manner as above may be controlled in some degree by controlling the drying condition or the kind and the content of the component in the composition that is a forming material for the resin layer, but differ from grooves to be formed through embossed pattern transfer, and it may be said that “it is substantially impossible to reproduce exactly the same shapes”. Consequently, the one or more concave portions formed through self-formation of a resin layer can be said to have irregular shapes.

The process of forming one or more concave portions on the surface (α) of the resin layer that the pressure sensitive adhesive sheet of the present invention has is considered to be as follows.

First, in formation of a coating film of a composition that is to be a forming material for the resin layer, and in the step of drying the coating film, contraction stress occurs inside the coating film, and in the part where the bonding force of the resin is weakened, the coating film may crack inside it. With that, the resin around the cracked part may temporarily flow into the space formed by the cracking, and it is considered that one or more concave portions may be formed on the surface (α) of the resin layer.

After two layers of coating films each having a different resin content are formed, the two layers of coating films are dried simultaneously, and it is considered that in drying them, a contraction stress difference may be generated inside the coating films to facilitate cracking of the coating films.

From the viewpoint of readily forming the one or more concave portions, it is recommended to control the condition appropriately in consideration of the following matters. It is considered that these matters could react with each other in a complex form to facilitate the formation of the one or more concave portions. In this connection, preferred embodiments of the matters for facilitating the formation of the one or more concave portions are as described in the corresponding sections to be given hereinunder.

The kind, constituent monomers, molecular weight and content of the resin contained in the composition of the forming material for the coating film.

The kind of the crosslinking agent and the kind of the solvent contained in the composition of the forming material for the coating film.

The viscosity and the solid concentration of the composition of the forming material for the coating film.

The thickness of the coating film to be formed (when plural layers are formed, the thickness of each coating film).

The drying temperature and the drying time for the formed coating film.

In formation of the pressure sensitive adhesive layer in an ordinary pressure sensitive adhesive sheet, it is intended to form the pressure sensitive adhesive layer having a flat surface, and the above-mentioned matters are suitably settled in many cases.

On the other hand, in the present invention, the above matters are so settled that the one or more concave portions capable of contributing toward improvement of the air escape property of the pressure sensitive adhesive sheet can be formed, quite differing from those in the planning method for the pressure sensitive adhesive layer of ordinary pressure sensitive adhesive sheets.

Preferably, the above-mentioned matters are suitably settled in consideration of the flowability of the resin contained in the coating film to be formed.

With respect to a composition containing fine particles, for example, by controlling the viscosity of the coating film formed of the composition containing a large amount of fine particles to fall within a suitable range, it is possible to suitably prevent the formed coating film from being mixed with any other coating film (a coating film containing a large amount of resin) while the predetermined flowability of the fine particles in the coating film could be maintained as such. By such controlling, cracks could be readily formed in the horizontal direction to facilitate formation of one or more concave portions in the coating film containing a large amount of resin.

As a result, it may be possible to increase the proportion of the one or more concave portions to be formed on the surface (α) and to increase the proportion of the one or more concave portions connecting to each other, thereby giving a pressure sensitive adhesive sheet having a more superior air escape property.

Among the above-mentioned matters, it is desirable to suitably control the kind, the constituent monomers and the molecular weight of the resin and the resin content so that the resin contained in the coating film containing a large amount of resin could have a suitable viscoelasticity.

Namely, by suitably increasing the hardness of the coating film (the hardness thereof that may be determined various factors such as the viscoelasticity of resin, the viscosity of the coating liquid, etc.), the contract stress of the resin part (X) increases to facilitate the formation of one or more concave portions. When the hardness of the coating film is higher, the contraction stress could be higher to facilitate the formation of one or more concave portions, but when the coating film is too hard, the coatability thereof may worsen. In addition, when the resin elasticity is increased too much, the adhesive strength of the resin layer to be formed from the coating film tends to lower. In consideration of these, it is desirable to suitably control the viscoelasticity of the resin.

With respect to a composition or a coating film containing fine particles, by suitably selecting the fine particles and the resin to thereby make the dispersion condition of the fine particles appropriate, the degree of swelling of the thickness of the resin layer owing to the fine particles therein and the self-forming power of the one or more concave portions could be thereby controlled and, as a result, the one or more concave portions could be readily formed on the surface (α).

Further, in consideration of the crosslinking speed of the formed coating film (or the composition of the forming material), it is desirable that the above-mentioned matters are suitably settled.

Namely, in the case where the crosslinking speed of the coating film is too high, the coating film would be cured before formation of one or more concave portions therein. In addition, in the case, there may be some influences on the degree of cracking of the coating film.

The crosslinking speed of the coating film may be controlled by suitably defining the kind of the crosslinking agent and the kind of the solvent in the composition of the forming material or by suitably settling the drying time and the drying temperature for the coating film.

Preferably, the resin layer is formed of a multilayer structure having a fine particles-containing layer that contains fine particles, and there may be mentioned a configuration of a layer having a multilayer structure formed by laminating a layer (Xβ) mainly containing a resin part (X), a layer (Y1) containing a particle part (Y) [fine particles-containing layer], and a layer (Xα) mainly containing a resin part (X) in this order from the side of a substrate or a release material, like in the pressure sensitive adhesive sheet 1 a in FIG. 1. The layer (Y1) containing a particle part (Y) preferably contains a particle part (Y) in an amount of 15 mass % or more.

The configuration of the multilayer structure mentioned above may also be a mixed layer configuration where the boundary between the layer (Xβ) and the layer (Y1), and/or the boundary between the layer (Y1) and the layer (Xα) could not be discerned.

In the resin layer 12, preferably, the layer (Xβ) is a layer of a composition containing a resin as a main component, the layer (Y1) is a layer of a composition containing fine particles and the layer (Xα) is a layer of a composition containing a resin as a main component.

The layer (Xβ) and the layer (Xα) are layers mainly containing the resin part (X) but may also contain a particle part (Y). However, the content of the particle part (Y) in the layer (Xβ) and the layer (Xα) is each independently less than 15% by mass relative to the total mass (100% by mass) of the layer (Xβ) or the layer (Xα) and is smaller than the content of the resin constituting the resin part (X).

The layer (Xβ) and the layer (Xα) may have a void part (Z) to be mentioned hereinunder, in addition to the resin part (X) and the particle part (Y).

The content of the resin in the layer (Xβ) and the layer (Xα) is each independently generally 50 to 100% by mass, and is preferably 65 to 100% by mass, more preferably 75 to 100% by mass, even more preferably 85 to 100% by mass, still more preferably 90 to 100% by mass, relative to the total mass (100% by mass) of the layer (Xβ) or the layer (Xα).

In the present invention, the “content of the resin in the layer (Xβ) and the layer (Xα)” may be considered to be the content of the resin in the total amount (100% by mass (but excluding diluent solvent)) of the resin composition that is the forming material for the layer (Xβ) or the layer (Xα).

The content of the fine particles constituting the particle part (Y) in the layer (Xβ) and the layer (Xα) is each independently less than 15% by mass relative to the total mass (100% by mass) of the layer (Xβ) or the layer (Xα), but is preferably 0 to 13% by mass, more preferably 0 to 10% by mass, even more preferably 0 to 5% by mass, still more preferably 0% by mass, relative to the total mass (100% by mass) of the layer (Xβ) or the layer (Xα).

In the present invention, the “content of the fine particles in the layer (Xβ) and the layer (Xα) may be considered to be the content of the fine particles in the total amount (100% by mass (but excluding diluent solvent)) of the resin composition that is the forming material for the layer (Xβ) or the layer (Xα).

Preferably, the layer (Xβ) and the layer (Xα) each are a layer formed of a composition (xβ) or (xα) containing a resin as a main component to be mentioned hereinunder.

The layer (Y1) containing the particle part (Y) may be a layer formed of the particle part (Y) alone or may also be a layer containing the resin part (X) along with the particle part (Y), and may further has a void part (Z) to be mentioned hereinunder.

The content of the fine particles constituting the particle part (Y) in the layer (Y1) is 15% by mass or more relative to the total mass (100% by mass) of the layer (Y1), but is preferably 20 to 100% by mass, more preferably 25 to 90% by mass, even more preferably 30 to 85% by mass, still more preferably 35 to 80% by mass, relative to the total mass (100% by mass) of the layer (Y1).

In the present invention, the “content of the fine particles in the layer (Y1)” may also be considered to be the content of the fine particles in the total amount (100% by mass (but excluding diluent solvent)) of the composition that is the forming material for the layer (Y1).

The content of the resin in the layer (Y1) is generally 1 to 85% by mass, and is preferably 5 to 80% by mass, more preferably 10 to 75% by mass, even more preferably 20 to 70% by mass, still more preferably 25 to 65% by mass, relative to the total mass (100% by mass) of the layer (Y1).

In the present invention, the “content of the resin in the layer (Y1)” may also be considered to be the content of the resin in the total amount (100% by mass (but excluding diluent solvent)) of the composition that is the forming material for the layer (Y1).

Preferably, the layer (Y1) is formed of a composition (y) containing fine particles in an amount of 15% by mass or more to be mentioned hereinunder.

As shown by FIG. 1 (a) to FIG. 1 (d), the pressure sensitive adhesive sheet of the present invention has one or more concave portions 13 on the surface (α) of the resin layer 12 on the side opposite to the side on which the substrate 11 or the release material 14 is provided. The one or more concave portions 13 existing on the surface (α) also play a role of air-discharge channels for removing outside the “air accumulation” to be formed in adhering the pressure sensitive adhesive sheet of the present invention to an adherend.

The length of the concave portion 13 in a planar view of the concave portion 13 existing on the surface (α) is not specifically limited. Namely, the concave portion 13 includes a relatively long groove-like one and a relatively short pit-like one.

In the pressure sensitive adhesive sheet of the present invention, the plural concave portions 13 existing on the surface (α) preferably satisfies the following requirements (I) to (III).

Requirement (I): Plural concave portions having a maximum height difference of 0.5 μm or more exist in a region (P) surrounded by an arbitrarily selected square having an edge length of 5 mm on the surface (α).

Requirement (II): 95% or more of plural concave portions having a maximum height difference of 0.5 μm or more existing inside a region (P) surrounded by an arbitrarily selected square having an edge length of 5 mm on the surface (α) have shapes differing from each other.

Requirement (III): One or more concave portions having a maximum height difference of 0.5 μm or more exist in a region (Q) surrounded by an arbitrarily selected square having an edge length of 1 mm on the surface (α).

Further, one embodiment of the pressure sensitive adhesive sheet of the present invention preferably satisfies at least one of the following requirements (IV) and (V), more preferably satisfies both the following requirements (IV) and (V).

Requirement (IV): Plural concave portions having a maximum height difference of 0.5 μm or more exist irregularly on the surface (α).

Requirement (V): One or more attached faces on the surface (α) of the resin layer has an irregular shape.

Requirement (VI): Plural attached faces exist on the surface (α) of the resin layer.

The requirements (I) to (VI) are described in detail hereinunder.

<Requirement (I)>

FIG. 2 includes schematic cross-sectional views of a resin layer, showing examples of a shape on the side of the surface (α) of the resin layer that the pressure sensitive adhesive sheet of the present invention has.

Like the concave portion 13 shown in FIG. 2(a), the shape of an ordinary concave portion has two mountain parts (M₁) and (M₂) and a valley part (N). The “height difference” of the concave portion in the present invention means the length of the difference (h) between the highest position (m) of the two mountain parts (M₁) and (M₂) (in FIG. 2(a), the maximum point of the mountain part (M₁)) and the lowest position (n) thereof (in FIG. 2(a), the minimum point of the valley part (N)), relative to the thickness direction of the resin layer 12.

It is considered that the case of FIG. 2(b) would have two concave portions of a concave portion 131 having two mountain parts (M₁₁) and (M₁₂) and a valley part (N₁), and a concave portion 132 having two mountain parts (M₁₂) and (M₁₃) and a valley part (N₂). In this case, the length of the difference (h₁) between the maximum point of the mountain part (M₁₁) and the minimum point of the valley part (N₁) indicates the height difference of the concave portion 131, and the length of the difference (h₂) between the maximum point of the mountain part (M₁₃) and the minimum point of the valley part (N₂) indicates the height difference of the concave portion 132.

In the present invention, the “one or more concave portions” existing on the surface (α) are the one or more concave portions having a maximum height difference of 0.5 μm or more. The “one or more concave portions” as defined in the present invention may be one having a site with a height difference of 0.5 μm or more in any part of the concave portion, and the one or more concave portions need not to have the height difference in the entire region thereof.

Regarding the presence or absence of plural concave portions satisfying the requirement (I), the region (P) surrounded by a square having an edge length of 5 mm that is arbitrarily selected on the surface (α) of the resin layer of the pressure sensitive adhesive sheet is observed with an electronic microscope for the judgment. More specifically, the presence or absence is judged according to the method described in the section of Examples.

The maximum value of the height difference of one concave portion is, from the viewpoint of improving the air escape property of the pressure sensitive adhesive sheet, from the viewpoint of keeping the appearance of the pressure sensitive adhesive sheet good, and from the viewpoint of the shape stability of the pressure sensitive adhesive sheet, preferably 1.0 μm or more and not more than the thickness of the resin layer, more preferably 3.0 μm or more and not more than the thickness of the resin layer, and even more preferably 5.0 μm or more and not more than the thickness of the resin layer.

The ratio of the maximum height difference of plural concave portions existing inside the region (P) to the thickness of the resin layer [maximum height difference/thickness of resin layer] is preferably 1/100 to 100/100, more preferably 5/100 to 99/100, even more preferably 10/100 to 96/100, still more preferably 15/100 to 90/100.

The mean value of the width of the concave portions is, from the viewpoint of improving the air escape property of the pressure sensitive adhesive sheet and from the viewpoint of bettering the pressure sensitive adhesiveness of the pressure sensitive adhesive sheet, preferably 1 to 500 μm, more preferably 3 to 400 pmn, even more preferably 5 to 300 μm.

In the present invention, the width of the concave portion means the distance between the maximum points of the two mountain parts, and in the concave portion 13 shown in FIG. 2(a), the width indicates the distance L between the mountain part (M₁) and the mountain part (M₂). In the concave portion 131 shown in FIG. 2(b), the width indicates the distance L₁ between the mountain part (M₁₁) and the mountain part (M₁₂), and in the concave portion 132 therein, the width indicates the distance L₂ between the mountain part (M₁₃) and the mountain part (M₁₂).

In a planar view of the pressure sensitive adhesive sheet of the present invention (when the sheet is viewed from directly above), when the concave portion has a long wide and a short side, the short side is the width.

The ratio of the maximum height difference of one concave portion to the mean value of the width [maximum height difference/mean value of width) (in the concave portion 13 shown in FIG. 2(a), the ratio is “h/L”) is, from the viewpoint of improving the air escape property of the pressure sensitive adhesive sheet and from the viewpoint of bettering the pressure sensitive adhesiveness of the pressure sensitive adhesive sheet, preferably 1/500 to 100/1, more preferably 3/400 to 70/3, even more preferably 1/60 to 10/1.

<Requirement (II)>

The requirement (II) means that 95% or more of plural concave portions having a maximum height difference of 0.5 μm or more existing inside a region (P) surrounded by a square having an edge length of 5 mm that is arbitrarily selected on the surface (α) have shapes differing from each other.

FIG. 3 shows one example of a schematic plan view of the surface (α) of the resin layer that the pressure sensitive adhesive sheet of the present invention has. As shown in FIG. 3, in the pressure sensitive adhesive sheet of the present invention, the ratio of the one or more concave portions that have shapes differing from each other to the plural one or more concave portions 13 existing on the surface (α) 12 a of the resin layer 12 is extremely large.

Regarding the matter whether or not the requirement (II) is satisfied, for example, a pressure sensitive adhesive sheet having, on the surface of the pressure sensitive adhesive layer thereof, grooves as arranged in a predetermined pattern in a preplanned shape as described in PTL 1 is definitely differentiated from the pressure sensitive adhesive sheet of the present invention. Namely, the plural concave portions 13 are different from grooves having a shape designed in advance, such as those formed with a release material having an embossed pattern thereon.

Regarding a heretofore-known pressure sensitive adhesive sheet having, on the surface of the pressure sensitive adhesive layer thereof, grooves as arranged in a predetermined pattern in a preplanned shape, even when at least one characteristic thereof selected from the air escape property, the outward appearance, the pressure sensitive adhesion characteristics and the punching property is tried to be improved by the shape of the grooves and the arrangement of the grooves, the other characteristics of the sheet are worsened in many cases.

The present inventors have specifically noted that, for example, the shape of the grooves capable of contributing toward improving air escape property and the shape of the grooves capable of improving pressure sensitive adhesion characteristics differs from each other, and have found out the technical meaning of satisfying the requirement (II).

Namely, in the pressure sensitive adhesive sheet of the present invention, the plural concave portions having shapes differing from each other and existing inside the region (P) on the surface (α) of the resin layer differ from each other also in point of the contribution ratio of the air escape property, the outward appearance, the pressure sensitive adhesion characteristics and the punching property. However, by forming such plural concave portions each having a different contribution ratio to those characteristics on the surface (α) of the resin layer, the characteristics of the resultant pressure sensitive adhesive sheet can be thereby well-balanced.

In one embodiment of the pressure sensitive adhesive sheet of the present invention, the ratio of the plural concave portions having shapes differing from each other and existing inside the region (P) on the surface (α) of the resin layer is preferably 98% or more relative to the total number (100%) of the concave portions existing inside the region (P), more preferably 100%.

In the present invention, the matter whether or not the requirement (II) is satisfied may be judged as follows. The shapes of the plural concave portions having a maximum height difference of 0.5 μm or more and existing inside the region (P) surrounded by a square having an edge length of 5 mm that is arbitrarily selected on the surface (α) of the resin layer of the targeted pressure sensitive adhesive sheet are observed with an electronic microscope (magnification: 30 to 100), and when the number of the concave portions having shapes differing from each other is 95% or more (preferably 98% or more, more preferably 100%) relative to the total number (100%) of the plural concave portions existing inside the region (P), it is judged that the observed sheet is a pressure sensitive adhesive sheet having a resin layer where concave portions satisfying the above requirement (II) exist on the surface (α) thereof. For the observation of the shapes of the plural concave portions, a method of directly observing the sheet with an electronic microscope having the above-mentioned magnification may be employed, or a method of taking a picture of the sheet using an electronic microscope having the above-mentioned magnification, and visually observing the shapes of the plural concave portions shown on the image may also be employed. More specifically, the satisfaction of the requirement may be judged according to the method described in the section of Examples.

Here, “the number of the concave portions having shapes differing from each other is 100%” means that “all the plural concave portions observed inside the region (P) have shapes differing from each other”.

In this description, the concave portions connected uninterruptedly to each other in a selected region are counted as “one concave portion”. However, when two concave portions existing in a selected region bonds to one concave portion in the other region adjacent to that selected region to form one concave portion, the two concave portions in the selected region should be counted as independent ones.

From the viewpoint of providing a pressure sensitive adhesive sheet having well-balanced characteristics of air escape property, appearance, pressure sensitive adhesion characteristics and punching property, it is preferable that the plural concave portions exist irregularly in the region (P) on the surface (α) of the resin layer of one embodiment of the pressure sensitive adhesive sheet of the present invention.

From the viewpoint of providing a pressure sensitive adhesive sheet having well-balanced characteristics of air escape property, appearance, pressure sensitive adhesion characteristics and punching property, it is preferable that the shapes of the one or more attached faces that exist in the region (P) on the surface (α) of the resin layer of one embodiment of the pressure sensitive adhesive sheet of the present invention have irregular shapes.

In the present invention, “one or more attached faces existing in the region (P) on the surface (α) of the resin layer” means a surface except the range occupied by plural concave portions in the region (P) on the surface (α) of the resin layer, and means a face to be kept in contact with an adherend in attaching to the adherend. FIG. 3(a) shows a schematic plan view of one example of the surface (α) of the resin layer that one embodiment of the pressure sensitive adhesive sheet of the present invention has, and the “one or more attached faces” indicates the shaded part except the plural concave portions 13 in the surface (α) 12 a of the resin layer shown in FIG. 3.

In the pressure sensitive adhesive sheet satisfying the requirement (II), it is considered that the shapes of the one or more attached faces existing inside the region (P) on the surface (α) would have irregular shapes.

For judgement whether or not “the shapes of the one or more attached faces existing in the region (P) on the surface (α) have irregular shapes”, the shapes of the one or more attached faces existing in the region (P) surrounded by an arbitrarily selected square having an edge length of 5 mm on the surface (α) of the resin layer of the targeted pressure sensitive adhesive sheet are observed with an electron microscope (magnification: 30 to 100) and then is determined from the shapes of the one or more attached faces.

However, for the observation of the shapes of the one or more attached faces, a direct observation method with an electron microscope at the above-mentioned magnification may be employed, or a method of taking an image with an electron microscope at the magnification followed by visually observing the shapes of the one or more attached faces on the image may also be employed.

<Requirement (III)>

FIG. 3 (a) and FIG. 3 (b) each are a schematic plan view of the surface (α), showing one example of the surface (α) of the resin layer that the pressure sensitive adhesive sheet of the present invention has. As shown in FIG. 3(a), plural concave portions 13 and 130 exist on the surface (α) 12 a of the resin layer 12 of the pressure sensitive adhesive sheet of the present invention.

Here, the pressure sensitive adhesive sheet of the present invention preferably has, as in the above-mentioned requirement (III), one or more concave portions 13 and 130 having a maximum height difference of 0.5 μm or more in the region (Q) surrounded by a square 50 having an edge length of 1 mm (hereinafter, the 1-mm square 50) that is arbitrarily selected on the surface (α) 12 a of the resin layer 12 therein. In FIG. 3(a), eight concave portions exist in the region (Q).

In that manner, presence of one or more concave portions each having a maximum height difference of 0.5 μm or more in the region (Q) on the surface (α) improves the air escape property of the pressure sensitive adhesive sheet.

In the present invention, the number of the concave portions existing in the region (Q) on the surface (α) is one or more, but is, from the above-mentioned viewpoint, preferably 2 or more, more preferably 3 or more, and on the other hand, from the viewpoint of bettering the appearance and the pressure sensitive adhesion characteristics, the number is preferably 1000 or less, more preferably 500 or less.

From the viewpoint of improving the air escape property of the pressure sensitive adhesive sheet, it is preferable that one or more of the above-mentioned concave portions 13 and 130 existing in the region (Q on the surface (α) 12 a of the resin layer 12 that one embodiment of the pressure sensitive adhesive sheet of the present invention has extend toward any side of the 1-mm square 50 that is a boundary line of the region (Q), as in FIG. 3(a)

On the surface (α) 12 a of the resin layer 12 of the pressure sensitive adhesive sheet shown by FIG. 3(a), the number of the cross lines 13 a between the extending concave portion 13 or 130 and any side of the 1-mm square 50 that is a boundary line of the region (Q) is 9 as a whole.

The number of the cross lines between the concave portion and any side of the 1-mm square 50 that is a boundary line of the region (Q) is preferably 1 or more, more preferably 2 or more, even more preferably 3 or more.

From the viewpoint of providing a pressure sensitive adhesive sheet having more improved air escape property, one or more concave portions existing in the region (Q) on the surface (α) of the resin layer that one embodiment of the pressure sensitive adhesive sheet of the present invention has preferably have a shape that continuously extends into the other one or more regions (Q′) surrounded by a 1-mm square adjacent to the region (Q), more preferably have a shape that continuously extends into the other two or more regions (Q′), and even more preferably have a shape that continuously extends into the other three or more regions (Q′),

For example, in FIG. 3(b), the region (Q) surrounded by the 1-mm square 50 that is arbitrarily selected on the surface (α) 12 a of the resin layer 12 is specifically noted. The “other region (Q′) surrounded by a square having an edge length of 1 mm that is adjacent to the region (Q)” indicates the region (Q′1) surrounded by the square 501 having an edge length of 1 mm (hereinafter, 1-mm square 501), the region (Q′2) surrounded by the square 502 having an edge length of 1 mm (hereinafter, 1-mm square 502), the region (Q′3) surrounded by the square 503 having an edge length of 1 mm (hereinafter, 1-mm square 503), and the region (Q′4) surrounded by the square 504 having an edge length of 1 mm (hereinafter, 1-mm square 504).

Further, the “concave portion 130” existing on the surface (α) 12 a of the resin layer 12 shown in FIG. 3(b) is specifically noted. The “concave portion 130” is a region existing in the region (Q) surrounded by the 1-mm square 50, and has a shape extending into the region (Q′1) surrounded by the square 501 having an edge length of 1 mm adjacent to the region (Q), into the region (Q′2) surrounded by the 1-mm square 502, and into the region (Q′4) surrounded by the 1-mm square 504.

Presence of the concave portion having a shape extending not only into the region (Q) but also into the other region (Q′) adjacent to the region (Q) on the surface (α), like the “concave portion 130” shown in FIG. 3(b), provides a pressure sensitive adhesive sheet having more improved air escape property.

In addition, it is preferable that the concave portions existing in the region (Q) on the surface (α) of the resin layer have a shape extending not only into one or more other region (Q′) adjacent to the region (Q) but also further continuously into any other regions (Q″) than the region (Q), which are adjacent to the other region (Q′).

For example, the “concave portion 130” shown in FIG. 3(b) has a shape extending not only into the region (Q′4) adjacent to the region (Q) but also further continuously into the region (Q′5) adjacent to the region (Q′4).

<Requirement (IV)>

In one embodiment of the pressure sensitive adhesive sheet of the present invention, preferably, plural concave portions having a maximum height difference of 0.5 μm or more exist irregularly on the surface (α) of the resin layer, like the above-mentioned requirement (IV).

In the present invention, the wording “plural concave portions exist irregularly” means a state where the positions of plural concave portions are at random not having the same recurring pattern (a state where the positions of plural concave portions do not have any periodicity). Namely, the state differs from a state of “arrangement” based on specific regularity, like that for the grooves described in PTL 1, that is, like that for grooves formed through embossed pattern transfer of pressing a release material having an embossed pattern to the surface of a resin layer.

Irregular existence of plural concave portions provides a pressure sensitive adhesive sheet having well-balanced characteristics of air escape property and pressure sensitive adhesion characteristics.

For the judgement whether or not “plural concave portions exist irregularly”, in principle, the positions of the plural concave portions existing on the surface (α) of the resin layer of the targeted pressure sensitive adhesive sheet are identified through visual observation thereof or through observation thereof with a digital microscope or an electron microscope (magnification: 30 to 100).

However, for the judgement, it is also possible that, on the surface (α), a region surrounded by an arbitrarily selected square of 1 to 10 mm on a side (preferably a region (P) surrounded by a square having an edge length of 5 mm) is selected, and the positions of the plural concave portions existing in the region are observed with a digital microscope or an electron microscope (magnification: 30 to 100 times). Namely, when the “positions of plural concave portions” existing inside the selected region do not have any specific regularity, the targeted pressure sensitive adhesive sheet can be considered to satisfy the requirement (IV).

For the observation of the positions at which the plural concave portions are formed, a method of direct observation thereof with a digital microscope or an electron microscope at the magnification as mentioned above may be employed, or a method of taking an image thereof with a digital microscope or an electron microscope having the above-mentioned magnification, followed by visually observing the forming positions of the plural concave portions shown in the image may also be employed.

In the present invention, as the digital microscope, for example, “Digital Microscope VHX-1000” or “Digital Microscope VHX-5000”, both trade names manufactured by Keyence Corporation may be used.

<Requirement (V)>

In one embodiment of the pressure sensitive adhesive sheet of the present invention, it is preferable that the shapes of the one or more attached faces on the surface (α) of the resin layer have irregular shapes, as in the above-mentioned requirement (V).

In the present invention, “one or more attached faces on the surface (α)” means a surface from which the range occupied by the plural concave portions on the surface (α) of the resin layer is excluded, and means a face that is to be attached to an adherend when an adherend is attached thereto.

In the schematic plan view of FIG. 3(a), the “one or more attached faces” indicates the shaded part excluding the plural concave portions 13 in the surface (α) 12 a of the resin layer.

The wording “the shapes of the one or more attached faces have irregular shapes” means that the shapes of the one or more attached faces are shapes not having any specific shape surrounded by a circle or a straight line alone (triangle, square, etc.) and not having any predetermined recurring pattern, like the shape of the shaded part of the surface (α) 12 a of the resin layer shown in FIG. 3(a). Namely, shapes of the one or more attached faces to be formed through embossed pattern transfer of pressing a release material having an embossed pattern against the surface of the resin layer are excluded.

In other words, in the pressure sensitive adhesive sheet satisfying the requirement (II) and the requirement (IV), it is considered that the shapes of the one or more attached faces on the surface (α) of the resin layer would have irregular shapes.

For judgement of whether or not “the shapes of the one or more attached faces on the surface (α) have irregular shapes”, in principle, the shapes of the one or more attached faces on the surface (α) of the resin layer of the targeted pressure sensitive adhesive sheet are observed visually or with a digital microscope or an electron microscope (magnification: 30 to 100).

However, for the judgement, a region surrounded by a square of 1 to 10 mm on a side arbitrarily selected on the surface (α) (preferably the region (P) surrounded by a 5-mm square) is selected, and the position of the plural concave portions existing in the region may be observed with a digital microscope or an electron microscope (magnification: 30 to 100). In other words, in the case where the “shapes of the one or more attached faces” in the selected region is judged to have irregular shapes, it may be considered that the targeted pressure sensitive adhesive sheet satisfies the requirement (V).

In addition, the observation of the shapes of the one or more attached faces may also be carried out according to a method of observing it directly with a digital microscope or an electron microscope at the above-mentioned magnification, or a method of taking a picture with a digital microscope or an electron microscope at the above-mentioned magnification followed by visually observing the shapes of the one or more attached faces shown on the image.

<Requirement (VI)>

Preferably, one embodiment of the pressure sensitive adhesive sheet of the present invention has plural attached faces on the surface (α) of the resin layer therein, as in the above-mentioned requirement (VI). The definition for the “one or more attached faces on the surface (α)” in the present invention is the same as in the above-mentioned requirement (V).

Regarding the judgement of whether or not plural attached faces exist, in principle, the shapes of the one or more attached faces on the surface (α) of the resin layer of the targeted pressure sensitive adhesive sheet may be observed visually or with a digital microscope or an electron microscope (magnification: 30 to 100), like in the requirement (V).

However, for the judgement, a region surrounded by a square of 1 to 10 mm on a side arbitrarily selected on the surface (α) (preferably the region (P) surrounded by a square having an edge length of 5 mm) is selected, and the shapes of the one or more attached faces in the region may be observed with a digital microscope or an electron microscope (magnification: 30 to 100).

In addition, the observation of the shapes of the one or more attached faces may also be carried out according to a method of observing it directly with a digital microscope or an electron microscope at the above-mentioned magnification, or a method of taking a picture with a digital microscope or an electron microscope at the above-mentioned magnification followed by visually observing the shapes of the one or more attached faces shown on the image.

In the following, each constitution of the pressure sensitive adhesive sheet of the present invention will be described.

Substrate

The substrate used in one embodiment of the present invention is not particularly limited, and examples thereof include a paper substrate, a resin film or sheet, and a substrate containing a paper substrate laminated with a resin, which may be appropriately selected depending on the purpose of the pressure sensitive adhesive sheet according to one embodiment of the present invention.

Examples of paper constituting the paper substrate include thin paper, medium quality paper, wood-free paper, impregnated paper, coated paper, art paper, parchment paper, and glassine paper.

Examples of the resin constituting the resin film or sheet include a polyolefin resin, such as polyethylene and polypropylene; a vinyl resin, such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, an ethylene-vinyl acetate copolymer, and an ethylene-vinyl alcohol copolymer; a polyester resin, such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene; an acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; polycarbonate; a urethane resin, such as polyurethane and acrylic-modified polyurethane; polymethylpentene; polysulfone; polyether ether ketone; polyether sulfone; polyphenylenesulfide; a polyimide resin, such as polyether imide and polyimdie; a polyamide resin; an acrylic resin; and a fluorine resin.

Examples of the substrate containing a paper substrate laminated with a resin include laminated paper containing the aforementioned paper substrate laminated with a thermoplastic resin, such as polyethylene.

Among these substrates, a resin film or sheet is preferred, a film or sheet formed of a polyester resin is more preferred, and a film or sheet formed of polyethylene terephthalate (PET) is further preferred.

In the case where the pressure sensitive adhesive sheet of the present invention is applied to a purpose that requires heat resistance, a film or sheet constituted by a resin selected from polyethylene naphthalate and a polyimide resin is preferred, and in the case where the pressure sensitive adhesive sheet is applied to a purpose that requires weather resistance, a film or sheet constituted by a resin selected from polyvinyl chloride, polyvinylidene chloride, an acrylic resin, and a fluorine resin is preferred.

The thickness of the substrate may be appropriately determined depending on the purpose of the pressure sensitive adhesive sheet of the present invention, and is preferably from 5 to 1,000 μm, more preferably from 10 to 500 μm, further preferably from 12 to 250 μm, and still further preferably from 15 to 150 μm, from the standpoint of the handleability and the economic efficiency.

The substrate may further contain various additives, such as an ultraviolet ray absorbent, a light stabilizer, an antioxidant, an antistatic agent, a slipping agent, an antiblocking agent, and a colorant.

The substrate used in one embodiment of the present invention is preferably a non-air permeable substrate from the standpoint of enhancing the blister resistance of the resulting pressure sensitive adhesive sheet, and specifically a substrate containing the aforementioned resin film or sheet having a metal layer on the surface thereof.

Examples of the metal forming the metal layer include a metal having metallic gloss, such as aluminum, tin, chromium, and titanium.

Examples of the method of forming the metal layer include a method of vapor-depositing the metal by a PVD method, such as vacuum vapor deposition, sputtering, and ion plating, and a method of attaching a metal foil formed of the metal with an ordinary pressure sensitive adhesive, and a method of vapor-depositing the metal by a PVD method is preferred.

In the case where a resin film or sheet is used as the substrate, the surface of the resin film or sheet may be subjected to a surface treatment by an oxidizing method, a roughening method, and the like, or may be subjected to a primer treatment, from the standpoint of enhancing the adhesion to the resin layer to be laminated on the resin film or sheet.

Examples of the oxidizing method include a corona discharge treatment, a plasma discharge treatment, a chromic acid treatment (wet process), a hot air treatment, and an ozone treatment, and an ultraviolet ray irradiation treatment, and examples of the roughening treatment include a sand blasting treatment and a solvent treatment.

Release Material

The release material used in one embodiment of the present invention may be a release sheet having both surfaces subjected to a release treatment, and a release sheet having one surface subjected to a release treatment, and examples thereof include a substrate for the release material having coated thereon a release agent. The release treatment is preferably performed on a flat release material without a relief shape formed thereon (for example, a release material having no emboss pattern formed thereon).

Examples of the substrate for the release material include the paper substrate, the resin film or sheet, and the substrate containing a paper substrate laminated with a resin described above used as the substrate of the pressure sensitive adhesive sheet according to one embodiment of the present invention.

Examples of the release agent include a rubber elastomer, such as a silicone resin, an olefin resin, an isoprene resin, and a butadiene resin, a long-chain alkyl resin, an alkyd resin, and a fluorine resin.

The thickness of the release material is not particularly limited, and is preferably from 10 to 200 μm, more preferably from 25 to 170 μm, and further preferably from 35 to 80 μm.

Resin Layer

Preferably, the resin layer that the pressure sensitive adhesive sheet of the present invention has, as existing on at least one surface thereof, one or more concave portions formed not through embossed pattern transfer, and contains a resin part (X) containing a resin as a main component and a particle part (Y) containing fine particles.

In the pressure sensitive adhesive sheet of the present invention, at least a surface (α) of the resin layer on the side opposite to the side on which a substrate or a release material is provided has pressure sensitive adhesiveness, and the surface (β) of the resin layer on the side on which a substrate or a release material is provided may also have pressure sensitive adhesiveness.

Preferably, the resin layer that one embodiment of the pressure sensitive adhesive sheet of the present invention additionally has a void part (Z) in addition to the resin part (X) and the particle part (Y). The void part (Z), if any, in the resin layer can improve the blister resistance of the pressure sensitive adhesive sheet.

The void part (Z) includes the voids existing between the fine particles and, when the fine particles are secondary particles, the voids existing inside the secondary particles.

In the case where the resin layer has a multilayer structure, even though a void part (Z) exists in the process of forming the resin layer or just after formation of the layer, the resin part (X) may flow into the void part (Z) and therefore the voids may disappear to give a resin layer not having the void part (Z).

However, even in the case where a void part (Z) having existed in the resin layer for a period of time has disappeared, the resin layer that one embodiment of the pressure sensitive adhesive sheet of the present invention has may have one or more concave portions on the surface (α) and can be therefore excellent in air escape property and blister resistance.

The shear storage elastic modulus at 100° C. of the resin layer that one embodiment of the pressure sensitive adhesive sheet of the present invention has is, from the viewpoint of improving the air escape property and the blister resistance of the pressure sensitive adhesive sheet, preferably 9.0×10³ Pa or more, more preferably 1.0×10⁴ Pa, even more preferably 2.0×10⁴ Pa or more.

In the present invention, the shear storage elastic modulus at 100° C. of the resin layer means a value measured with a viscoelastometer (for example, apparatus name “DYNAMIC ANALYZER RDA II” manufactured by Rheometrics Inc.) at a frequency of 1 Hz.

The thickness of the resin layer is preferably 1 to 300 μm, more preferably 5 to 150 μm, even more preferably 10 to 75 μm.

The adhesive strength of the surface (α) of the resin layer of one embodiment of the pressure sensitive adhesive sheet of the present invention is preferably 0.5 N/25 mm or more, more preferably 2.0 N/25 mm or more, even more preferably 3.0 N/25 mm or more, further more preferably 4.0 N/25 mm or more, still further more preferably 7.0 N/25 mm or more.

In the case where the surface (β) of the resin layer also has pressure sensitive adhesiveness, the adhesive strength of the surface (β) preferably belongs to the above-mentioned range.

The value of the adhesive strength of the pressure sensitive adhesive sheet means a value measured according to the method described in the section of Examples.

<Resin Part (X)>

The resin part (X) constituting the resin layer contains a resin as a main component.

In the present invention, the resin part (X) is a part containing any other component than fine particles contained in the resin layer, and in this point, this is differentiated from the particle part (Y).

The resin part (X) contains a resin as a main component and may contain a crosslinking agent and ordinary additives in addition to resin.

The content of the resin in the resin part (X) is generally 40% by mass or more, and is preferably 50% by mass or more, more preferably 65% by mass or more, even more preferably 75% by mass or more, still more preferably 85% by mass or more, further more preferably 90% by mass or more, relative to the total amount (100% by mass) of the resin part (X), and is preferably 100% by mass or less, more preferably 99.9% by mass or less, relative to the total amount (100% by mass) of the resin part (X).

In the present invention, a value of the content of the resin in the resin composition to be the forming material for the resin part (X) may be considered to be the above-mentioned “content of the resin in the resin part (X)”.

The resin to be contained in the resin part (X) is preferably a pressure sensitive adhesive resin from the viewpoint of making the surface (α) of the resin layer to be formed express pressure sensitive adhesiveness.

In particular, in the case where the resin layer has a multilayer structure formed by laminating a layer (Xβ), a layer (Y1) and a layer (Xα) in this order from the side on which a substrate or a release material is provided, like in the pressure sensitive adhesive sheet 1 a of FIG. 1(a), it is desirable from the above-mentioned viewpoints that at least the layer (Xα) contains a pressure sensitive adhesive resin.

Examples of the pressure sensitive adhesive resin include acrylic resins, urethane resins, rubber resins, silicone resins, etc.

Among these pressure sensitive adhesive resins, an acrylic resin is preferably contained from the viewpoint that the pressure sensitive adhesion characteristics and the weather resistance thereof are good and that plural concave portions satisfying the above-mentioned requirements (I) to (III) are easy to form on the surface (α) of the resin layer to be formed.

The content of the acrylic resin is preferably 25 to 100% by mass, and is more preferably 50 to 100% by mass, even more preferably 70 to 100% by mass, still more preferably 80 to 100% by mass, further more preferably 100% by mass, relative to the total amount (100% by mass) of the resin contained in the resin part (X).

From the viewpoint that plural concave portions satisfying the above-mentioned requirements (I) to (III) are easy to form on the surface (α) of the resin layer to be formed, it is desirable that the resin part (X) contains a resin having a functional group, more preferably an acrylic resin having a functional group.

In particular, in the case where the resin layer has a multilayer structure formed by laminating a layer (Xβ), a layer (Y1) and a layer (Xα) in this order from the side on which a substrate or a release material is provided, like in the pressure sensitive adhesive sheet 1 a of FIG. 1(a), it is desirable from the above-mentioned viewpoints that at least the layer (Y1) contains a resin having a functional group.

The functional group is a group to be a crosslinking start point with a crosslinking agent, and examples thereof include a hydroxy group, a carboxy group, an epoxy group, an amino group, a cyano group, a keto group, an alkoxysilyl group, etc., but a carboxyl group is preferred.

Also preferably, the resin part (X) further contains a crosslinking agent along with the resin having a functional group. In particular, in the case where the resin layer has the above-mentioned multilayer structure, it is desirable that at least the layer (Y1) contains a crosslinking agent along with the above-mentioned, functional group-having resin.

Examples of the crosslinking agent include an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent, etc.

Examples of the isocyanate crosslinking agent include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, etc.; aliphatic polyisocyanates such as hexamethylene diisocyanate, etc.; alicyclic polyisocyanates such as isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, etc.; biuret forms and isocyanurate forms of these compounds, and adduct forms that are reaction products with a low-molecular active hydrogen-containing compounds (ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, etc.); etc.

Examples of the epoxy crosslinking agent include ethylene glycol glycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N′,N′-tetraglycidyl-m-xylylenediamine, 1,6-hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, diglycidylamine, etc.

Examples of the aziridine crosslinking agent include diphenylmethane-4,4′-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane tri-β-aziridinylpropionate, toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), tris-1-(2-methylaziridine) phosphine, trimethylolpropane tri-β-(2-methylaziridine)propionate, etc.

The metal chelate crosslinking agent includes chelate compounds where the metal atom is aluminium, zirconium, titanium, zinc, iron, tin or the like. From the viewpoint that plural concave portions satisfying the above requirements (I) to (III) are easy to form, an aluminium chelate crosslinking agent is preferred.

Examples of the aluminium chelate crosslinking agent include diisopropoxyaluminium monooleyl acetacetate, monoisopropropoxyaluminium bisoleyl acetacetate, monoisopropoxyalumiium monooleate monoethylacetacetate, diisopropoxyaluminium monolauroyl acetacetate, diisopropoxyaluminium monostearyl acetacetate, diisopropoxyaluminium monoisostearyl acetacetate, etc.

One alone or two or more of these crosslinking agents may be used either singly or as combined.

Among these, from the viewpoint that plural concave portions satisfying the above requirements (I) to (III) are easy to form on the surface (α) of the resin layer to be formed, it is desirable that the resin part (X) contains one or more selected from a metal chelate crosslinking agent, an epoxy crosslinking agent and an aziridine crosslinking agent, more preferably contains a metal chelate crosslinking agent, and even more preferably contains an aluminium chelate crosslinking agent.

The content of the crosslinking agent is preferably 0.01 to 15 parts by mass, and is more preferably 0.1 to 10 parts by mass, even more preferably 0.3 to 7.0 parts by mass, relative to 100 parts by mass of the resin having a functional group.

From the viewpoint of bettering the shape retentive force of the plural concave portions on the surface (α) of the resin layer, it is desirable that the resin part (X) contains both a metal chelate crosslinking agent and an epoxy crosslinking agent.

In the case where the resin part (X) contains both a metal chelate crosslinking agent and an epoxy crosslinking agent, the content ratio by mass of the metal chelate crosslinking agent to the epoxy crosslinking agent [metal chelate crosslinking agent/epoxy crosslinking agent] in the resin part (X) is, from the above-mentioned viewpoints, preferably 10/90 to 99.5/0.5, more preferably 50/50 to 99.0/1.0, even more preferably 65/35 to 98.5/1.5, further more preferably 75/25 to 98.0/2.0.

The resin part (X) may contain any ordinary additive.

Examples of the ordinary additive include a tackifier, an antioxidant, a softener (plasticizer), a rust inhibitor, a pigment, a dye, a retardant, a reaction accelerator, a UV absorbent, etc.

One alone or two or more of these ordinary additives may be used either singly or as combined.

In the case where these ordinary additives are contained, the content of each ordinary additive is preferably 0.0001 to 60 parts by mass, and is more preferably 0.001 to 50 parts by mass, relative to 100 parts by mass of the resin.

One alone or two or more resins may be contained in the resin part (X) either singly or as combined.

The forming material for the resin part (X) of the resin layer that the pressure sensitive adhesive sheet of the present invention has is preferably a pressure sensitive adhesive containing a pressure sensitive adhesive resin having a functional group, more preferably an acrylic pressure sensitive adhesive containing an acrylic resin (A) having a functional group (hereinafter this may be simply referred to as “acrylic resin (A)”), and even more preferably an acrylic pressure sensitive adhesive containing a functional group-having acrylic resin (A) and a crosslinking agent (B).

The acrylic pressure sensitive adhesive may be any of a solvent-type one or an emulsion-type one.

The acrylic pressure sensitive adhesive favorable for the forming material for the resin part (X) is described below.

Examples of the acrylic resin (A) contained in the acrylic pressure sensitive adhesive include a polymer having a structural unit derived from an alkyl (meth)acrylate having a linear or branched alkyl group, a polymer having a structural unit derived from a (meth)acrylate having a cyclic structure, etc.

The mass-average molecular weight (Mw) of the acrylic resin (A) is preferably 50,000 to 1,500,000, more preferably 150,000 to 1,300,000, even more preferably 250,000 to 1,100,000, still more preferably 350,000 to 900,000.

Preferably, the acrylic resin (A) contains an acrylic copolymer (A1) having a structural unit (a1) derived from an alkyl (meth)acrylate (a1′) having an alkyl group with 1 to 18 carbon atoms (hereinafter this may be referred to as “monomer (a1′)”), and a structural unit (a2) derived from a functional group-containing monomer (a2′) (hereinafter this may be referred to as “monomer (a2′)”), and more preferably contains an acrylic copolymer (A1).

The content of the acrylic copolymer (A1) is preferably 50 to 100% by mass, and is more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, further more preferably 90 to 100% by mass, relative to the total amount (100% by mass) of the acrylic resin (A) in the acrylic pressure sensitive adhesive.

The copolymerization morphology of the acrylic copolymer (A1) is not specifically limited, and the copolymer may be any of a block copolymer, a random copolymer or a graft copolymer.

The carbon number of the alkyl group that the monomer (a1′) has is, from the viewpoint of improving pressure sensitive adhesion characteristics, more preferably 4 to 12, even more preferably 4 to 8, further more preferably 4 to 6.

Examples of the monomer (a1′) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, etc.

Among these, butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred, and butyl (meth)acrylate is more preferred.

The content of the structural unit (a1) is preferably 50 to 99.5% by mass, and is more preferably 60 to 99% by mass, even more preferably 70 to 95% by mass, still more preferably 80 to 93% by mass, relative to all the structural units (100% by mass) of the acrylic copolymer (A1).

Examples of the monomer (a2′) include a hydroxy group-containing monomer, a carboxy group-containing monomer, an epoxy group-containing monomer, an amino group-containing monomer, a cyano group-containing monomer, a keto group-containing monomer, an alkoxysilyl group-containing monomer, etc.

Among these, a carboxy group-containing monomer is more preferred.

The carboxy group-containing monomer includes (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, etc., and (meth)acrylic acid is preferred.

The content of the structural unit (a2) is preferably 0.5 to 50% by mass, and is more preferably 1 to 40% by mass, even more preferably 5 to 30% by mass, still more preferably 7 to 20% by mass, relative to all the structural units (100% by mass) of the acrylic copolymer (A1).

The acrylic copolymer (A1) may have a structural unit (a3) derived from any other monomer (a3′) than the above-mentioned monomers (a1′) and (a2′).

Examples of the other monomer (a3′) include (meth)acrylates having a cyclic structure such as cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, imido(meth)acrylate, etc.; vinyl acetate, acrylonitrile, styrene, etc.

The content of the structural unit (a3) is preferably 0 to 30% by mass, and is more preferably 0 to 20% by mass, even more preferably 0 to 10% by mass, still more preferably 0 to 5% by mass, relative to all the structural units (100% by mass) of the acrylic copolymer (A1).

One alone or two or more of the above-mentioned monomers (a1′) to (a3′) may be used either singly or as combined.

A method for synthesis of the acrylic copolymer (A1) component is not specifically limited. For example, the copolymer may be produced according to a method including dissolving starting monomers in a solvent and polymerizing them in a mode of solution polymerization in the presence of a polymerization initiator, a chain transfer agent and the like, or a method of emulsion polymerization in an aqueous system using starting monomers in the presence of an emulsifier, a polymerization initiator, a chain transfer agent, a dispersant, etc.

The crosslinking agent (B) to be contained in the acrylic pressure sensitive adhesive includes those mentioned hereinabove, but from the viewpoint of bettering pressure sensitive adhesion characteristics and from the viewpoint of facilitating the formation of plural concave portions satisfying the above-mentioned requirements (I) to (III) on the surface (α) of the resin layer to be formed, at least one or more selected from a metal chelate crosslinking agent, an epoxy crosslinking agent and an aziridine crosslinking agent are preferably contained, more preferably a metal chelate crosslinking agent is contained, and even more preferably an aluminium chelate crosslinking agent is contained.

From the viewpoint of bettering the shape retentivity of plural concave portions on the surface (α) of the resin layer, the crosslinking agent (B) preferably contains both a metal chelate crosslinking agent and an epoxy crosslinking agent.

The content of the crosslinking agent (B) is preferably 0.01 to 15 parts by mass, and is more preferably 0.1 to 10 parts by mass, even more preferably 0.3 to 7.0 parts by mass, relative to 100 parts by mass of the acrylic resin (A) in the acrylic pressure sensitive adhesive.

In the case where a metal chelate crosslinking agent and an epoxy crosslinking agents are used as combined, the content ratio by mass of the metal chelate crosslinking agent to the epoxy crosslinking agent [metal chelate crosslinking agent/epoxy crosslinking agent] is preferably 10/90 to 99.5/0.5, more preferably 50/50 to 99.0/1.0, even more preferably 65/35 to 98.5/1.5, further more preferably 75/25 to 98.0/2.0.

The acrylic pressure sensitive adhesive to be used in one embodiment of the present invention may contain any ordinary additive within a range not detracting from the advantageous effects of the present invention. The general additive includes those mentioned hereinabove, and the content of the ordinary additive is also as mentioned above.

The acrylic pressure sensitive adhesive to be used in one embodiment of the present invention may contain any other pressure sensitive adhesive resin than the acrylic resin (A) (for example, urethane resin, rubber resin, silicone resin, etc.) within a range not detracting from the advantageous effects of the present invention.

The content of the acrylic resin (A) in the acrylic pressure sensitive adhesive is preferably 50 to 100% by mass, and is more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, still more preferably 100% by mass, relative to the total amount (100% by mass) of the pressure sensitive adhesive resin contained in the acrylic pressure sensitive adhesive.

<Particle Part (Y)>

The particle part (Y) constituting the resin layer is formed of fine particles.

The mean particle size of the fine particles is, from the viewpoint of improving the air escape property and the blister resistance of the pressure sensitive adhesive sheet and from the viewpoint of facilitating the formation of plural concave portions satisfying the above requirements (I) to (III) on the surface (α) of the resin layer to be formed, preferably 0.01 to 100 μm, more preferably 0.05 to 25 μm, even more preferably 0.1 to 10 μm.

The fine particles to be used in one embodiment of the present invention are not specifically limited, including inorganic particles such as silica particles, metal oxide particles, barium sulfate, calcium carbonate, magnesium carbonate, glass beads, smectite and the like, and organic particles such as acrylic beads, etc.

Among these fine particles, one or more selected from silica particles, metal oxide particles and smectite are preferred, and silica particles are more preferred.

The silica particles that are used in one embodiment of the present invention may be any ones of dry-method silica and wet-method silica.

The silica particles that are used in one embodiment of the present invention may also be an organic-modified silica that has been surface-modified with an organic compound having a reactive functional group or the like, an inorganic-modified silica that has been surface-treated with an inorganic compound such as sodium aluminate, sodium hydroxide or the like, as well as an organic/inorganic-modified silica that has been surface-treated with any of these organic compounds and inorganic compounds, or an organic/inorganic-modified silica that has been surface-treated with an organic/inorganic hybrid material of a silane coupling agent, etc.

These silica particles may be in the form of a mixture of two or more kinds.

The mass concentration of silica in the silica particles is preferably 70 to 100% by mass, and is more preferably 85 to 100% by mass, even more preferably 90 to 100% by mass, relative to the total amount (100% by mass) of the silica particles.

The volume-average secondary particle diameter of the silica particles that are used in one embodiment of the present invention is, from the viewpoint of improving the air escape property and the blister resistance of the pressure sensitive adhesive sheet, and from the viewpoint of facilitating the formation of plural concave portions satisfying the above requirements (I) to (III) on the surface (α) of the resin layer to be formed, preferably 0.5 to 10 μm, more preferably 1 to 8 μm, even more preferably 1.5 to 5 μm.

In the present invention, the value of the volume-average secondary particle diameter of the silica particles is a value determined through measurement of particle size distribution according to a Coulter counter method using Multisizer III or the like.

Examples of the metal oxide particles include particles of a metal oxide selected from titanium oxide, alumina, boehmite, chromium oxide, nickel oxide, copper oxide, titanium oxide, zirconium oxide, indium oxide, zinc oxide, and composite oxides thereof, etc., and include sol particles of those metal oxides.

Examples of smectite include montmorillonite, beidellite, hectorite, saponite, stevensite, nontronite, sauconite, etc.

The mass retention rate after heating the resin layer that one embodiment of the pressure sensitive adhesive sheet of the present invention has, at 800° C. for 30 minutes is preferably 3 to 90% by mass, more preferably 5 to 80% by mass, even more preferably 7 to 70% by mass, still more preferably 9 to 60% by mass.

The mass retention rate can be considered to indicate the content (% by mass) of the fine particles contained in the resin layer.

When the mass retention rate is 3% by mass or more, the pressure sensitive adhesive sheet can be excellent in air escape property and blister resistance. In addition, in production of the pressure sensitive adhesive sheet of the present invention, plural concave portions satisfying the requirements (I) to (III) can be readily formed on the surface (α) of the resin layer to be formed. On the other hand, when the mass retention rate is 90% by mass or less, a pressure sensitive adhesive sheet can be provided in which the film strength of the resin layer is high and which is excellent in water resistance and chemical resistance.

[Production Method for Pressure Sensitive Adhesive Sheet]

A production method for the pressure sensitive adhesive sheet of the present invention is described below.

The production method for the pressure sensitive adhesive sheet of the present invention is not specifically limited, but from the viewpoint of productivity and from the viewpoint of facilitating the formation of plural concave portions satisfying the above requirements (I) to (III) on the surface (α) of the resin layer to be formed, a method having at least the following steps (1) and (2) is preferred.

Step (1): a step of forming a coating film (x′) of a composition (x) containing the resin as a main component, and a coating film (y′) of a composition (y) containing the fine particles preferably in an amount of 15% by mass or more

Step (2): a step of drying the coating film (x′) and the coating film (y′) formed in the step (1) simultaneously

<Step (1)>

The step (1) is a step of forming a coating film (x′) of a composition (x) containing the resin as a main component, and a coating film (y′) of a composition (y) containing the fine particles preferably in an amount of 15% by mass or more.

The composition (x) is a forming material for the resin part (X), and preferably contains a crosslinking agent along with the above-mentioned resin, and may further contain the above-mentioned ordinary additive.

The composition (y) is a forming material for the particle part (Y), and may contain a resin and a crosslinking agent, as well as the above-mentioned ordinary additive. The composition (y) containing those components of resin and others could also be a forming material for the resin part (X).

(Composition (x))

The resin contained in the composition (x) includes a resin that constitutes the above-mentioned resin part (X), and is preferably a pressure sensitive adhesive resin having a functional group, more preferably the above-mentioned functional group-having acrylic resin (A), and is preferably the above-mentioned acrylic copolymer (A1).

The content of the resin in the composition (x) is generally 40% by mass or more, and is preferably 50% by mass or more, more preferably 65% by mass or more, even more preferably 75% by mass or more, still more preferably 85% by mass or more, further more preferably 90% by mass or more, relative to the total amount (100% by mass (but excluding diluent solvent)) of the composition (x), and is preferably 100% by mass or less, more preferably 95% by mass or less, relative to the total amount (100% by mass (but excluding diluent solvent)) of the composition (x).

The crosslinking agent contained in the composition (x) includes the crosslinking agent contained in the above-mentioned resin part (X). Preferably, one or more selected from a metal chelate crosslinking agent, an epoxy crosslinking agent and an aziridine crosslinking agent are contained, and more preferably a metal chelate crosslinking agent is contained.

Further, from the viewpoint of bettering the shape retentivity of the plural concave portions on the surface (α) of the resin layer to be formed, it is desirable that the composition (x) contains both a metal chelate crosslinking agent and an epoxy crosslinking agent.

In the case where the composition (x) contains both a metal chelate crosslinking agent and an epoxy crosslinking agent, the content ratio by mass of the metal chelate crosslinking agent to the epoxy crosslinking agent in the composition (x) [metal chelate crosslinking agent/epoxy crosslinking agent] is preferably 10/90 to 99.5/0.5, more preferably 50/50 to 99.0/1.0, even more preferably 65/35 to 98.5/1.5, still more preferably 75/25 to 98.0/2.0.

The content of the crosslinking agent is preferably 0.01 to 15 parts by mass, and is more preferably 0.1 to 10 parts by mass, even more preferably 0.3 to 7.0 parts by mass, relative to 100 parts by mass of the resin contained in the composition (x).

Preferably, the composition (x) is an acrylic pressure sensitive adhesive containing the above-mentioned functional group-having acrylic resin (A) and crosslinking agent (B), more preferably an acrylic pressure sensitive adhesive containing the above-mentioned acrylic copolymer (A1) and crosslinking agent (B).

The details of the acrylic pressure sensitive adhesive are as mentioned above.

The composition (x) may contain the above-mentioned fine particles, in which the content of the fine particles is less than 15% by mass and is smaller than the content of the resin contained in the composition (x).

Specifically, the content of the fine particles is less than 15% by mass, and is preferably 0 to 13% by mass, more preferably 0 to 10% by mass, even more preferably 0 to 5% by mass, still more preferably 0% by mass, relative to the total amount (100% by mass (but excluding diluent solvent)) of the composition (x).

(Composition (y))

The composition (y) is a forming material for the particle part (Y), and contains at least the above-mentioned fine particles generally in an amount of 15% by mass or more, but from the viewpoint of the dispersibility of the fine particles therein, the composition preferably contains a resin along with the fine particles, and more preferably further contains a crosslinking agent along with the rein. The composition (y) may contain any ordinary additive.

These resin, crosslinking agent and ordinary additive may be the forming material for the resin part (X).

The fine particles to be contained in the composition (y) include those mentioned hereinabove, and from the viewpoint of forming the void part (Z) in the resin layer to provide a pressure sensitive adhesive sheet having improved blister resistance, one or more kinds selected from silica particles, metal oxide particles and smectite are preferred.

The content of the fine particles in the composition (y) is, from the viewpoint of facilitating the formation of irregular concave portions on the surface (α) of the resin layer through self-formation of the resin layer, preferably 15% by mass or more, and is preferably 20 to 100% by mass, more preferably 25 to 90% by mass, even more preferably 30 to 85% by mass, still more preferably 35 to 80% by mass, relative to the total amount (100% by mass (but excluding diluent solvent)) of the resin composition (y).

The resin to be contained in the composition (y) includes the same ones as those of the resin to be contained in the above-mentioned composition (x), and preferably contains the same resin as in the composition (x). One alone or two or more kinds of these resins may be used either singly or as combined.

More specifically, the resin to be contained in the composition (y) is preferably a resin having a functional group, more preferably the above-mentioned functional group-having acrylic resin (A), even more preferably the above-mentioned acrylic copolymer (A1).

The content of the resin in the composition (y) is generally 1 to 85% by mass, and is preferably 5 to 80% by mass, more preferably 10 to 75% by mass, even more preferably 20 to 70% by mass, further more preferably 25 to 65% by mass, relative to the total amount (100% by mass (but excluding diluent solvent)) of the composition (y).

The crosslinking agent to be contained in the composition (y) includes those of the crosslinking agent to be contained in the above-mentioned resin part (X), but preferably the composition (y) contains at least one or more selected from a metal chelate crosslinking agent, an epoxy crosslinking agent and an aziridine crosslinking agent, more preferably a metal chelate crosslinking agent. Also preferably, the composition (y) contains both a metal chelate crosslinking agent and an epoxy crosslinking agent.

In the case where the composition (y) contains both a metal chelate crosslinking agent and an epoxy crosslinking agent, a preferred range of the content ratio (by mass) of the metal chelate crosslinking agent to the epoxy crosslinking agent in the composition (y) is the same as in the above-mentioned composition (x).

The content of the crosslinking agent is preferably 0.01 to 15 parts by mass, and is more preferably 0.1 to 10 parts by mass, even more preferably 0.3 to 7.0 parts by mass, relative to 100 parts by mass of the resin contained in the composition (y).

(Formation Method for Coating Film (x′), (y′))

For facilitating the formation of a coating film, it is desirable that a solvent is incorporated in the composition (x) or (y) to give a solution of the composition.

The solvent includes water, organic solvents, etc.

Examples of the organic solvent include toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropyl alcohol, t-butanol, s-butanol, acetylacetone, cyclohexanone, n-hexane, cyclohexane, etc. One alone or two or more of these solvents may be used either singly or as combined.

The order of laminating the coating films (x′) and (y′) to be formed in this step is not specifically limited, but preferably, the coating film (x′) is laminated on the coating film (y′).

Regarding the formation method for the coating films (x′) and (y′), there may be employed a successive formation method of forming a coating film (y′) and then forming a coating film (x′) on the coating film (y′), or from the viewpoint of productivity, there may also be employed a simultaneous coating method of coating with both the coating film (y′) and the coating film (x′) using a multilayer coater.

Examples of the coater for use in successive formation include a spin coater, a spray coater, a bar coater, a knife coater, a roll coater, a knife roll coater, a blade coater, a gravure coater, a curtain coater, a die coater, etc.

Examples of the coater for use in simultaneous coating with a multilayer coater include a curtain coater, a die coater, etc., and among these, a die coater is preferred from the viewpoint of operability.

In this step (1), after the formation of at least one of the coating film (x′) and the coating film (y′) and prior to the step (2), pre-drying treatment may be carried out in such a degree that the curing reaction of the coating film could not go on.

The drying temperature in the pre-drying treatment in this step (1) is generally settled within a temperature range in which the formed coating film is not cured, but is preferably lower than the drying temperature in the step (2). A specific drying temperature indicated by the definition of indicating a range “lower than the drying temperature in the step (2)” is preferably 10 to 45° C., more preferably 10 to 34° C., even more preferably 15 to 30° C.

<Step (2)>

The step (2) is a step of drying the coating film (x′) and the coating film (y′) formed in the step (1) simultaneously.

In this step, the coating film (x′) and the coating film (y′) formed are dried simultaneously, whereby a resin layer containing the resin part (X) and the particle part (Y) is formed and in addition, plural concave portions are formed on the surface (ot) of the resin layer.

The drying temperature in this step is, from the viewpoint of facilitating the formation of plural concave portions satisfying the above-mentioned requirements (I) to (III) on the surface (α) of the resin layer to be formed, preferably 35 to 200° C., more preferably 60 to 180° C., even more preferably 70 to 160° C., still more preferably 80 to 140° C.

When the drying temperature is 35° C. or higher, a pressure sensitive adhesive sheet having good air escape property can be obtained. On the other hand, when the drying temperature is 200° C. or lower, the substrate and the release material that the pressure sensitive adhesive sheet has can be free from trouble of shrinkage thereof.

When the drying temperature is lower, the height difference of the concave portions to be formed could increase but the number of the concave portions to be formed tends to decrease.

In the vicinity of the particle part (Y) of the resin layer to be formed in this step, a void part (Z) may be formed.

The void part (Z) can be readily formed by using at least one or more kinds selected from silica particles, metal oxide particles and smectite as the fine particles to be contained in the composition (y).

In the case where a pressure sensitive adhesive sheet having a resin layer having a multilayer structure is produced in which the multilayer structure is formed by laminating a layer (Xβ) mainly containing the resin part (X), a layer (Y1) containing the particle part (Y) preferably in an amount of 15% by mass or more, and a layer (Xα) mainly containing the resin part (X) in this order, like the pressure sensitive adhesive sheet 1 a of FIG. 1(a), a production method of the following first and second embodiments is preferred.

In the description of the production method of the following first and second embodiments, the “composition (xβ) or (xα) containing a resin as a main component” is the same as the above-mentioned composition (x), and the details of the constituent components contained in the composition (xβ) or (xα) (kind of the component, preferred components, content of the component, etc.) are also the same as in the latter. The “composition (y) containing fine particles in an amount of 15% by mass or more” is also as mentioned above.

[Production Method of First Embodiment]

The production method of the first embodiment has at least the following steps (1A) and (2A).

Step (1A): a step of forming, on a substrate or a release material, a coating film (xβ′) of a composition (xβ) containing a resin as a main component, a coating film (y′) of a composition (y) containing fine particles preferably in an amount of 15% by mass or more and a coating film (xα′) of a composition (xα) containing a resin as a main component, as laminated thereon in this order

Step (2A): a step of drying the coating film (xβ′), the coating film (y′) and the coating film (xα′) formed in the step (1A) simultaneously

Also in the step (1A), it is desirable that the above-mentioned solvent is incorporated in the composition (xβ), the composition (y) and the composition (xα) to form solutions of the individual compositions, and the resultant solutions are used for coating.

Regarding the formation method for the coating film (xβ′), the coating film (y′) and the coating film (xα′), there may be employed a successive formation method of forming a coating film (xβ′) on a substrate or a release material, then forming a coating film (y′) on the coating film (xβ′), and further forming a coating film (xα′) on the coating film (y′), using the above-mentioned coater, or a simultaneous coating method of forming a coating film (xβ′), a coating film (y′) and a coating film (xα′), using the above-mentioned multilayer coater.

In the step (1A), after formation of one or more coating films of the coating film (xβ′), the coating film (y′) and the coating film (xα′) and prior to the step (2A), pre-drying treatment may be carried out in such a degree that the curing reaction of the coating films could not go on.

For example, after formation of the coating film (xβ′), the coating film (y′) and the coating film (xα′), such pre-drying treatment may be carried out every time after the formation, or after the formation of the coating film (xβ′) and the coating film (y′), the two may be subjected to the pre-drying treatment all together, and then the coating film (xα′) may be formed thereon.

In this step (1A), the drying temperature for the pre-drying treatment is generally so settled as to fall within a temperature range in which the formed coating film is not cured, but is preferably lower than the drying temperature in the step (2A). A specific drying temperature indicated by the definition of indicating a range “lower than the drying temperature in the step (2A)” is preferably 10 to 45° C., more preferably 10 to 34° C., even more preferably 15 to 30° C.

The step (2A) is a step of drying the coating film (xβ′), the coating film (y′) and the coating film (xα′) formed in the step (1A), simultaneously. The preferred range of the drying temperature in this step is the same as that in the above-mentioned step (2). In this step, a resin layer containing the resin part (X) and the particle part (Y) is formed.

[Production Method of Second Embodiment]

The production method of the second embodiment has at least the following steps (1B) and (2B).

Step (1B): a step of forming, on a layer (Xβ) mainly containing a resin part (X) that is provided on a substrate or a release material, a coating film (y′) of a composition (y) containing fine particles preferably in an amount of 15% by mass or more and a coating film (xα′) of a composition (xα) containing a resin as a main component, as laminated thereon in this order

Step (2B): a step of drying the coating film (y′) and the coating film (xα′) formed in the step (1B) simultaneously

In the step (1B), the “layer (Xβ) mainly containing a resin part (X)” is formed by drying the above-mentioned coating film (xβ′) of a composition (xβ) containing a resin as a main component.

Since the layer (Xβ) is formed of the composition (xβ), the layer (Xβ) may contain a crosslinking agent, an ordinary additive and others in addition to the resin therein. The content of the resin part (X) in the layer (Xβ) is as described above.

Regarding the formation method for the layer (Xβ), a coating film (xβ′) of a composition (xβ) containing a resin as a main component is formed on a substrate or a release material, and the coating film (xβ′) is dried to form the layer.

The drying temperature at this time is not specifically limited, but is preferably 35 to 200° C., more preferably 60 to 180° C., even more preferably 70 to 160° C., still more preferably 80 to 140° C.

This embodiment differs from the above-mentioned first embodiment in that the coating film (y′) and the coating film (xα′) are formed in this order on the layer (Xβ) formed by drying, but not on the coating film (xβ′).

Also in the step (1B), it is desirable that the above-mentioned solvent is incorporated in the composition (y) and the composition (xα) to form solutions of the respective compositions, and thereafter the solutions are used for coating.

Regarding the formation method for the coating film (y′) and the coating film (xα′), there may be employed a successive formation method of forming a coating film (y′) on the layer (Xβ) and then forming a coating film (xα′) on the coating film (y′), using the above-mentioned coater, or a simultaneous coating method of coating with both the coating film (y′) and the coating film (xα′) using a multilayer coater.

In the step (1B), after formation of the coating film (y′) or after formation of the coating film (y′) and the coating film (xα′) and prior to the step (2B), pre-drying treatment may be carried out in such a degree that the curing reaction of the coating films could not go on.

In this step (1B), the drying temperature for the pre-drying treatment is generally so settled as to fall within a temperature range in which the formed coating film is not cured, but is preferably lower than the drying temperature in the step (2B). A specific drying temperature indicated by the definition of indicating a range “lower than the drying temperature in the step (2B)” is preferably 10 to 45° C., more preferably 10 to 34° C., even more preferably 15 to 30° C.

The step (2B) is a step of drying the coating film (y′) and the coating film (xot′) formed in the step (1B) simultaneously, and the preferred range of the drying temperature in this step is the same as in the above-mentioned step (2). In this step, a resin layer containing the resin part (X) and the particle part (Y) is formed.

[Viscoelastic Layer of the Present Invention]

The viscoelastic layer of the present invention has, on at least one surface thereof, one or more concave portions formed not by transferring an emboss pattern, and corresponds to the resin layer in the pressure sensitive adhesive sheet of the present invention mentioned hereinabove. Accordingly, the configuration and the preferred embodiment of the viscoelastic layer of the present invention are the same as those of the resin layer in the pressure sensitive adhesive sheet.

EXAMPLES

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. The property values in the following examples and production examples are values measured by the following methods.

Mass Average Molecular Weight of Resin (Mw)

The measurement was performed by using a gel permeation chromatography instrument (“HLC-8020, a product name, produced by Tosoh Corporation) under the following conditions, and a value measured as the standard polystyrene conversion was used.

Measurement Condition

Column: “TSK guard column HXL-L”, “TSK gel G2500HXL”, “TSK gel G2000HXL”, and “TSK gel G1000HXL” (all produced by Tosoh Corporation), connected in series

Column temperature: 40° C.

Developing solvent: tetrahydrofuran

Flow rate: 1.0 mL/min

Measurement of Volume Average Secondary Particle Diameter of Silica Particles

The volume average secondary particle diameter of the silica particles was obtained by measuring the particle size distribution with Multisizer III (produced by Beckman Coulter Inc.) by the Coulter Counter method.

Measurement of Thickness of Resin Layer

The thickness of the resin layer was measured by observing the cross section of the resin layer of the target pressure sensitive adhesive sheet with a scanning electron microscope (“S-4700”, a product name, produced by Hitachi, Ltd.).

Production Examples x-1 to x-6

Preparation of Solutions (x-1) to (x-6) of Resin Composition

To 100 parts by mass of the solution of an acrylic resin with the kind and the solid content shown in Table 1, a crosslinking agent and a diluting solvent with the kinds and the mixed amounts shown in Table 1 were added, so as to prepare solutions (x-1) to (x-6) of a resin composition having the solid contents shown in Table 1.

The details of the components shown in Table 1 used for the preparation of the solutions (x-1) to (x-6) of a resin composition are as follows.

Solution of Acrylic Resin

Solution (i): a mixed solution of toluene and ethyl acetate containing an acrylic resin (x-i) (an acrylic copolymer having structural units derived from butyl acrylate (BA) and acrylic acid (AA), BA/AA=90/10 (% by mass), Mw: 470,000) having a solid concentration of 33.6% by mass

Solution (ii): a mixed solution of toluene and ethyl acetate containing an acrylic resin (x-ii) (an acrylic copolymer having structural units derived from butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA), vinyl acetate (VAc), and acrylic acid (AA), BA/2EHA/VAc/AA=46/37/10/7 (% by mass), Mw: 370,000) having a solid concentration of 43.0% by mass

Crosslinking Agent

Aluminum chelate crosslinking agent: “M-5A”, a product name, produced by Soken Chemical & Engineering Co., Ltd., solid concentration: 4.95% by mass

Epoxy crosslinking agent: a solution of an epoxy crosslinking agent obtained by diluting “TETRAD-C” (a product name, produced by Mitsubishi Gas Chemical Co., Inc.) with toluene to make a solid concentration of 5% by mass

Isocyanate crosslinking agent: “Coronate L”, a product name, produced by Tosoh Corporation, solid concentration: 75% by mass

Aziridine crosslinking agent: “BXX5134”, a product name, produced by Toyochem Co., Ltd., solid concentration: 5% by mass

Diluting Solvent

IPA: isopropyl alcohol

AcOEt: ethyl acetate

TABLE 1 Aluminum chelate crosslinking Epoxy crosslinking agent agent (M-5A, solid concentration: (TETRAD-C, solid Solution of acrylic resin 4.95 wt %) concentration: 5 wt %) Mixed Mixed Mixed amount amount Solid content amount Mixed of solid Mixed of solid per 100 parts Mixed of solid Solution of amount content amount content by mass of amount content resin (part by (part by (part by (part by acrylic resin (part by (part by composition Kind Kind of resin mass) mass) mass) mass) (part by mass) mass) mass) Production (x-1) solution (i) acrylic resin (x-i) 100 33.6 5   0.25 0.74 — — Example (BA/AA = 90/10 x-1 (wt %), Mw: 470,000 Production (x-2) solution (i) acrylic resin (x-i) 100 33.6 — — — — — Example (BA/AA = 90/10 x-2 (wt %), Mw: 470,000 Production (x-3) solution (ii) Acrylic resin (x-ii) 100 43.0 4.5 0.22 0.52 0.3 0.015 Example (BA/2EHA/VAc/AA = x-3 46/37/10/7 (wt %), Mw: 370,000 Production (x-4) solution (i) acrylic resin (x-i) 100 33.6 — — — 0.6 0.030 Example (BA/AA = 90/10 x-4 (wt %), Mw: 470,000 Production (x-5) solution (i) acrylic resin (x-i) 100 33.6 — — — — — Example (BA/AA = 90/10 x-5 (wt %), Mw: 470,000 Production (x-6) solution (i) acrylic resin (x-i) 100 33.6 — — — — — Example (BA/AA = 90/10 x-6 (wt %), Mw: 470,000 Epoxy cross- linking agent (TETRAD-C, Isocyanate crosslinking agent Aziridine crosslinking agent solid con- (Coronate L, solid concentration: (BXX5134, solid concentration: centration: 75 wt %) 5 wt %) 5 wt %) Mixed Mixed Solid content amount Solid content amount Solid content Solid per 100 parts Mixed of solid per 100 parts Mixed of solid per 100 parts concentration of by mass of amount content by mass of amount content by mass of Diluting solution of resin acrylic resin (part by (part by acrylic resin (part by (part by acrylic resin solvent composite (part by mass) mass) mass) (part by mass) mass) mass) (part by mass) Kind (% by mass) Production — — — — — — — IPA 28 Example x-1 Production — — — — — — — IPA 27 Example x-2 Production 0.035 — — — — — — IPA 34.4 Example x-3 Production 0.089 — — — — — — IPA 24 Example x-4 Production — 1.5 0.56 1.674 — — — AcOEt 28 Example x-5 Production — — — — 1.0 0.050 0.149 AcOEt 28 Example x-6

Production Example y-0

Preparation of Fine Particle Dispersion Liquid (y-0)

To 100 parts by mass (solid content: 33.6 parts by mass) of the solution (i) containing the acrylic resin (x-i) (a mixed solution of toluene and ethyl acetate containing an acrylic copolymer having structural units derived from butyl acrylate (BA) and acrylic acid (AA) (BA/AA=90/10 (% by mass), Mw: 470,000) having a solid concentration of 33.6% by mass), 50.4 parts by mass (solid content: 50.4 parts by mass) of silica particles (“Nipsil E-200A”, a product name, produced by Tosoh Silica Corporation, volume average secondary particle diameter: 3 μm) and toluene were added, and the fine particles were dispersed, so as to prepare a fine particle dispersion liquid (y-0) having a solid concentration of 30% by mass containing the acrylic resin and the silica particles.

Production Examples y-1 to y-8

Preparation of Coating Liquids (y-1) to (y-8) for Forming Coating Film (y′)

To the mixed amount shown in Table 2 of the fine particle dispersion liquid (y-0) produced in Production Example y-0, the kinds and the mixed amounts shown in Table 2 of the solution of an acrylic resin, the crosslinking agent, and the diluting solvent were added, so as to prepare coating liquids (y-1) to (y-8) for forming a coating film (y′) having the solid concentrations shown in Table 2.

The details of the components shown in Table 2 used for the preparation of the coating liquids (y-1) to (y-8) for forming a coating film (y′) are as follows.

Solution of Acrylic Resin

Solution (i): acrylic resin (x-i) (the details thereof are described above)

Crosslinking Agent

Aluminum chelate crosslinking agent: “M-5A”, a product name, produced by Soken Chemical & Engineering Co., Ltd., solid concentration: 4.95% by mass

Epoxy crosslinking agent: a solution of an epoxy crosslinking agent obtained by diluting “TETRAD-C” (a product name, produced by Mitsubishi Gas Chemical Co., Inc.) with toluene to make a solid concentration of 5% by mass

Diluting Solvent

IPA: isopropyl alcohol

IPA/CHN: mixed solvent containing isopropyl alcohol (IPA) and cyclohexanone (CHN) (IPA/CHN=60/40 (mass ratio))

TABLE 2 Fine particle dispersion liquid (y-0) Aluminum chelate cross- produced in Production Example y-0 linking agent (M-5A, (solid concentration: 30 wt %) Solution of acrylic resin solid concentration: 4.95 wt %) Mixed Mixed Mixed Coating amount Content of amount amount liquid for Mixed of solid fine Mixed of solid Mixed of solid forming amount content particles (*) amount content amount content coated (part by (part by (part by (part by (part by (part by (part by layer (y′) mass) mass) mass) Kind Kind or resin mass) mass) mass) mass) Production (y-1) 69.7 20.9 12.5 solution acrylic resin (x-i) 30.3 10.2 5.52 0.27 Example (i) (BA/AA = 90/10 y-1 (wt %), Mw: 470,000 Production (y-2) 61.6 18.5 11.1 solution acrylic resin (x-i) 38.4 12.9 6.04 0.30 Example (i) (BA/AA = 90/10 y-2 (wt %), Mw: 470,000 Production (y-3) 77.6 23.3 14.0 solution acrylic resin (x-i) 22.4 7.5 5.01 0.25 Example (i) (BA/AA = 90/10 y-3 (wt %), Mw: 470,000 Production (y-4) 85.4 25.6 15.4 solution acrylic resin (x-i) 14.6 4.9 4.51 0.22 Example (i) (BA/AA = 90/10 y-4 (wt %), Mw: 470,000 Production (y-5) 71.0 21.3 12.8 solution acrylic resin (x-i) 29.0 9.7 5.44 0.27 Example (i) (BA/AA = 90/10 y-5 (wt %), Mw: 470,000 Production (y-6) 69.7 20.9 12.5 solution acrylic resin (x-i) 30.3 10.2 — — Example (i) (BA/AA = 90/10 y-6 (wt %), Mw: 470,000 Production (y-7) 71.0 21.3 12.8 solution acrylic resin (x-i) 29.0 9.7 — — Example (i) (BA/AA = 90/10 y-7 (wt %), Mw: 470,000 Production (y-8) 71.0 21.3 12.8 solution acrylic resin (x-i) 29.0 9.7 2.72 0.13 Example (i) (BA/AA = 90/10 y-8 (wt %), Mw: 470,000 Aluminum chelate crosslinking agent (M-5A, solid con- Epoxy crosslinking agent centration: 4.95 wt %) (TETRAD-C, solid concentration: 5 wt %) Solid Solid content per Mixed content per Concentration 100 parts by amount 100 parts by Solid of fine particles mass of Mixed of solid mass of concentration in solid content acrylic resin amount content acrylic resin Diluting of coating of coating (part by (part by (part by (part by solvent liquid liquid (**) mass) mass) mass) mass) Kind (% by mass) (% by mass) Production 1.47 — — — IPA 27 40 Example y-1 Production 1.47 — — — IPA 27 35 Example y-2 Production 1.47 — — — IPA 27 45 Example y-3 Production 1.47 — — — IPA 27 50 Example y-4 Production 1.47 — — — IPA/ 26 41 Example CHN y-5 Production — — — — IPA 27 40 Example y-6 Production — 0.66 0.033 0.18 IPA 26 41 Example y-7 Production 0.74 0.33 0.017 0.09 IPA 26 41 Example y-8 (*): value calculated from (solid mixed amount) × 50.4/(50.4 + 33.6) (**): value calculated from (content of fine particles)/((solid mixed amount in fine particle dispersion liquid (y-0)) + (solid mixed amount of acrylic resin) + (solid mixed amount of aluminum chelate crosslinking agent) + (solid mixed amount of epoxy crosslinking agent)) × 100

Examples 1 to 8 (1) Formation of Coating Film

A polyethylene terephthalate (PET) film having an aluminum vapor deposition layer on one surface thereof (“FNS MAT N50”, a product name, produced by Lintec Corporation, thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, the solution (x-1) of a resin composition prepared in Production Example x-1 was coated with an applicator to the thickness shown in Table 3 as the thickness of the coating film after coating (i.e., the thickness of the coating film in a non-dried state), so as to form a coating film (xβ′).

Subsequently, on the coating film (xβ′) thus formed, one of the coating liquids (y-1) to (y-4) for forming a coating film (y′) of the kinds shown in Table 3 was coated with an applicator to the thickness shown in Table 3 as the total thickness after coating both the two layers, i.e., the coating film (xβ′) and a coating film (y′) (i.e., the total thickness of the two layers in a non-dried state), so as to form a coating film (y′).

Then, on the coating film (y′) thus formed, the solution (x-1) of a resin composition prepared in Production Example x-1 was coated with an applicator to the thickness shown in Table 3 as the total thickness after coating all the three layers, i.e., the coating film (xβ′), the coating film (y′), and a coating film (xα′) (i.e., the total thickness of the three layers in a non-dried state), so as to form a coating film (xα′).

(2) Drying Treatment

The three layers of the coating film (xβ′), the coating film (y′), and the coating film (xα′) were simultaneously dried at a drying temperature of 100° C. for 2 minutes, thereby producing a pressure sensitive adhesive sheet with a substrate, having a resin layer containing a resin part (X) and a particle part (Y) having the thickness shown in Table 3.

Example 9

A PET film having an aluminum vapor deposition layer on one surface thereof (“FNS MAT N50”, a product name, produced by Lintec Corporation, thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, the solution (x-2) of a resin composition prepared in Production Example x-2 was coated with a knife coater to a thickness of 25 μm as the thickness of the coating film after coating (i.e., the thickness of the coating film in a non-dried state), so as to form a coating film (xβ′), which was then dried at a drying temperature of 100° C. for 2 minutes, so as to form a layer (Xβ) containing a resin part (X).

Lamination was performed in such a manner that the surface of the layer (Xβ) thus formed was attached to a release agent layer of a release film (“SP-PET381031”, a product name, produced by Lintec Corporation, a PET film having a silicone release agent layer provided on one surface thereof, thickness: 38 μm), so as to produce once a laminated body having the layer (Xβ).

Subsequently, on the surface of the layer (Xβ) having been exposed by removing the release film of the laminated body, the coating liquid (y-1) for forming a coating film (y′) prepared in Production Example y-1 and the solution (x-1) of a resin composition prepared in Production Example x-1 were simultaneously coated with a multilayer die coater (width: 500 mm), so as to form a coating film (y′) and a coating film (xα′) simultaneously in this order on the layer (Xβ). The coated layers were formed to a thickness of 55 μm for the coating film (y′) and a thickness of 65 μm for the coating film (xα′) through the setting of the multilayer die coater.

Then, the two layers of the coating film (y′) and the coating film (xα′) were simultaneously dried at a drying temperature of 100° C. for 2 minutes, thereby producing a pressure sensitive adhesive sheet with a substrate, having a resin layer containing a resin part (X) and a particle part (Y) having the thickness shown in Table 3.

Comparative Example 1

A pressure sensitive adhesive sheet with a substrate, having a resin layer containing only a resin part (X) having a thickness of 25 μm was produced in the same manner as in Example 1, except that the coating film (y′) and the coating film (xα′) in Example 1 were not formed, but on the aluminum vapor deposition layer of the PET film used as the substrate, the solution (x-1) of a resin composition prepared in Production Example x-1 was coated with a knife coater to a thickness of 25 μm after drying to form a coating film (xβ′).

Comparative Example 2

A PET film having an aluminum vapor deposition layer on one surface thereof (“FNS MAT N50”, a product name, produced by Lintec Corporation, thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, the solution (x-1) of a resin composition prepared in Production Example x-1 was coated with an applicator to form a coating film (xβ′), which was then dried at 100° C. for 2 minutes, so as to form a layer (Xβ) containing a resin part (X) having a thickness of 5 μm.

Separately from the above, on a release agent layer of a release film (“SP-PET381031”, a product name, produced by Lintec Corporation, a PET film having a silicone release agent layer provided on one surface thereof, thickness: 38 μm), the coating liquid (y-1) for forming a coating film (y′) prepared in Production Example y-1 was coated with an applicator to form a coated layer (y′), which was then dried at 100° C. for 2 minutes, so as to form a layer (Y1) containing a resin part (X) and a particle part (Y) having a thickness of 15 μm.

Further separately from the above, on a release agent layer of a release film of the same kind as above, the solution (x-1) of a resin composition prepared in Production Example x-1 was coated with an applicator to form a coating film (xα′), which was then dried at 100° C. for 2 minutes, so as to form a layer (Xα) containing a resin part (X) having a thickness of 5 μm.

Then, lamination was performed in such a manner that the surface of the layer (Xβ) formed on the PET film as the substrate was attached to the exposed surface of the layer (Y1) thus formed. Furthermore, lamination was performed in such a manner that the surface of the layer (Y1) having been exposed by removing the release film on the layer (Y1) was attached to the exposed surface of the layer (Xα) thus formed.

According to the procedures, a pressure sensitive adhesive sheet with a substrate, having a resin layer containing a resin part (X) and a particle part (Y) having a thickness of 25 μm, containing the substrate having laminated in this order thereon the layer (Xβ), the layer (Y1), and the layer (Xα) was produced.

Examples 10 to 16

A PET film having an aluminum vapor deposition layer on one surface thereof (“FNS MAT N50”, a product name, produced by Lintec Corporation, thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, one of the solutions (x-1) to (x-6) of a resin composition prepared in Production Examples x-1 to x-6 and one of the coating liquids (y-1) to (y-8) for forming a coating film (y′) prepared in Production Examples y-1 to y-8 were simultaneously coated with a multilayer die coater (width: 250 mm) at the flow rate and the coating speed shown in Table 4, so as to form a coating film (xβ′), a coating film (y′), and a coating film (xα′) simultaneously in this order from the side of the substrate.

The kind of the solution of the resin composition and the kind of the coating liquid for forming a coated layer (y′) used as formation materials of the coating films are shown in Table 4.

The three layers of the coating film (xβ′), the coating film (y′), and the coating film (xα′) were simultaneously dried at a drying temperature of 100° C. for 2 minutes, thereby producing a pressure sensitive adhesive sheet with a substrate, having a resin layer containing a resin part (X) and a particle part (Y) having the thickness shown in Table 4.

Example 17

On a release agent layer of a release film (“SP-PET381031”, a product name, produced by Lintec Corporation, a PET film having a silicone release agent layer provided on one surface thereof, thickness: 38 μm) as a first release material, the solution (x-3) of a resin composition prepared in Production Example x-3, the coating liquid (y-5) for forming a coating film (y′) prepared in Production Example y-5, and the solution (x-3) of a resin composition prepared in Production Example x-3 were simultaneously coated in this order with a multilayer die coater (width: 250 mm) at the flow rate and the coating speed shown in Table 4, so as to form a coating film (xβ′), a coating film (y′), and a coating film (xα′) simultaneously in this order from the side of the release film.

Then, the three layers of the coating film (xβ′), the coating film (y′), and the coating film (xα′) were simultaneously dried at a drying temperature of 100° C. for 2 minutes, so as to form a resin layer containing a resin part (X) and a particle part (Y) having the thickness shown in Table 4. Then, lamination was performed in such a manner that the surface (α) of the resin layer thus formed was attached to a surface of a release agent layer of a release film (“SP-PET386040”, a product name, produced by Lintec Corporation) as a second release material, thereby producing a pressure sensitive adhesive sheet without a substrate.

Subsequently, after allowing to stand the pressure sensitive adhesive sheet without a substrate under an environment at 23° C. for one week, the first release material was removed, and lamination was performed in such a manner that the exposed surface (β) of the resin layer was attached to a surface of an aluminum vapor deposition layer of a PET film having an aluminum vapor deposition layer (“FNS MAT N50”, a product name, produced by Lintec Corporation, thickness: 50 μm) as a substrate, thereby providing a pressure sensitive adhesive sheet with a substrate.

Example 18

A PET film having an aluminum vapor deposition layer on one surface thereof (“FNS MAT N50”, a product name, produced by Lintec Corporation, thickness: 50 μm) was used as a substrate.

On the aluminum vapor deposition layer of the PET film, the solution (x-1) of a resin composition prepared in Production Example x-1 was coated with a knife coater to form a coating film (xβ′), which was then dried at 100° C. for 2 minutes, so as to form a layer (Xp) containing a resin part (X) having a thickness of 8 μm. Lamination was performed in such a manner that the surface of the layer (Xβ) thus formed was attached to a surface of a release agent layer of a release film (“SP-PET381031”, a product name, produced by Lintec Corporation, a PET film having a silicone release agent layer provided on one surface thereof, thickness: 38 μm), so as to produce once a laminated body having the layer (Xβ).

Subsequently, on the surface of the layer (Xβ) having been exposed by removing the release film of the laminated body, the coating liquid (y-1) for forming a coating film (y′) prepared in Production Example y-1 and the solution (x-1) of a resin composition prepared in Production Example x-1 were simultaneously coated in this order with a multilayer die coater (width: 500 mm) at the flow rate and the coating speed shown in Table 4, so as to form a coating film (y′) and a coating film (xα′) simultaneously in this order from the side of the layer (Xβ).

Then, the two layers of the coating film (y′) and the coating film (xα′) were simultaneously dried at a drying temperature of 100° C. for 2 minutes, thereby producing a pressure sensitive adhesive sheet with a substrate, having a resin layer containing a resin part (X) and a particle part (Y) having the thickness shown in Table 4.

The resin layers of the pressure sensitive adhesive sheets produced in Examples and Comparative Examples were subjected to the measurements and the evaluations shown below. The results are shown in Tables 3 and 4.

<Formation of One or More Concave Portions on Surface (α)>

A specific region defined by the requirements on the surface (α) of the resin layer of the pressure sensitive adhesive sheet produced in Examples and Comparative Examples was checked for formation of one or more concave portions satisfying the following requirements (I) to (III), using a scanning electron microscope (trade name “S-4700”, manufactured by Hitachi Limited, for the requirement (II), the magnification for observation was 30).

In Table 3 and Table 4, those judged to have one or more concave portions satisfying the requirements formed therein were given “A”, and those not judged to have one or more concave portions satisfying the requirements were given “F”.

Requirement (I): Plural concave portions having a maximum height difference of 0.5 μm or more exist in a region (P) surrounded by a square having an edge length of 5 mm that is arbitrarily selected on the surface (α).

Requirement (II): Relative to the total number (100%) of plural concave portions having a maximum height difference of 0.5 μm or more existing inside a region (P) surrounded by a square having an edge length of 5 mm that is arbitrarily selected on the surface (α), the number of the concave portions that have shapes differing from each other is 95% or more (in the case of 100%, that is, in the case where all the concave portions inside the region (P) have shapes differing from each other, the tested sheets were given “A+” in the Tables.)

Requirement (III): One or more concave portions having a maximum height difference of 0.5 μm or more exist in a region (Q) surrounded by an arbitrarily selected square having an edge length of 1 mm on the surface (α).

In evaluation of the requirement (I), a largest value of the measured plural height differences of the concave portions is referred to as “maximum height difference” as shown in Table 3 and Table 4.

Mass Retention Rate of Resin Layer of Pressure Sensitive Adhesive Sheet

For Examples and Comparative Examples except for Example 17, the resin layer was formed according to the method of the Examples and Comparative Examples on the surface of the release agent layer of a release film (“SP-PET381031”, a product name, produced by Lintec Corporation, a PET film having a silicone release agent layer provided on one surface thereof, thickness: 38 μm) instead of the substrate, and then the release film was removed, so as to provide a sole resin layer.

For Example 17, the two release films were removed from the pressure sensitive adhesive sheet without a substrate obtained in the course of the production, so as to provide a sole resin layer.

The resin layer before heating was measured for the mass thereof, and then heated to 800° C. for 30 minutes in a muffle furnace (“KDF-P90”, a product name, produced by Denken Co., Ltd.). The resin layer after heating was measured for the mass thereof, and the mass retention rate of the resin layer was calculated by the following expression.

mass retention rate of resin layer (%)=((mass of resin layer after heating)/(mass of resin layer before heating))×100

The pressure sensitive adhesive sheets produced in Examples and Comparative Examples were measured or evaluated for the “air escape property”, the “blister resistance”, and the “adhesive strength” according to the following methods. The results are shown in Tables 3 and 4.

Air Escape Property

The pressure sensitive adhesive sheet with a substrate in a size of 50 mm in length and 50 mm in width was attached to a melamine-coated plate as an adherend in a manner forming air accumulation. The presence of absence of the air accumulation after press-attaching with a squeegee was observed, and the air escape property of the pressure sensitive adhesive sheets was evaluated based on the following standard.

A: The air accumulation disappeared, and excellent air escape property was obtained.

F: The air accumulation remained, and poor air escape property was obtained.

Blister Resistance

The pressure sensitive adhesive sheet with a substrate in a size of 50 mm in length and 50 mm in width was attached to a polymethyl methacrylate plate having a size of 70 mm in length, 150 mm in width, and 2 mm in thickness (“Acrylite L001”, produced by Mitsubishi Rayon Co., Ltd.), followed by press-attaching with a squeegee, so as to provide a test specimen.

The test specimen was allowed to stand at 23° C. for 12 hours, then allowed to stand in a hot air dryer at 80° C. for 1.5 hours, further allowed to stand in a hot air dryer at 90° C. for 1.5 hours, and then visible to the naked eyes for the occurrence state of blister after the heat acceleration, and the blister resistance of the pressure sensitive adhesive sheets was evaluated based on the following standard.

A: Completely no blister was observed.

B: Blister was partially observed.

C: Blister was observed over the surface.

Adhesive Strength

The pressure sensitive adhesive sheets with a substrate produced in Examples and Comparative Examples were cut into a size of 25 mm in length and 300 mm in width, and the surface (α) of the resin layer of the pressure sensitive adhesive sheets was attached to a stainless steel plate (SUS304, polished with #360 polishing paper) under an environment of 23° C., 50% RH (relative humidity), followed by allowing to stand in the same environment for 24 hours. After standing, the adhesive strength of the pressure sensitive adhesive sheets was measured according to JIS Z0237:2000 by the 180° peeling method at a peeling speed of 300 mm/min.

TABLE 3 Coating film (y′) Thickness of coating film (μm) Coating Fine particle Coating Coating Coating film (xβ′) Kind of concentration in film (xα′) Resin layer Coating film (xβ′ + film (xβ′ + Kind of coating coating film (y′) Kind of Thickness film (xβ′) y′) y′ + xα′) solution liquid (% by mass) solution (μm) Example 1 25 75 100 (x-1) (y-1) 40 (x-1) 25.7 Example 2   12.5 75 100 (x-1) (y-1) 40 (x-1) 25.1 Example 3 25 50 100 (x-1) (y-1) 40 (x-1) 23.9 Example 4 25 200  250 (x-1) (y-1) 40 (x-1) 43.1 Example 5 25 75 100 (x-1) (y-2) 35 (x-1) 23.8 Example 6 25 75 100 (x-1) (y-3) 45 (x-1) 30.1 Example 7 25 75 100 (x-1) (y-4) 50 (x-1) 32.3 Example 8 25 200  250 (x-1) (y-2) 35 (x-1) 41.0 Example 9 25   80 (*1)   145 (*1) (x-2) (y-1) 40 (x-1) 42.0 Comparative   25⁽*²⁾ — — (x-1) — 0 — 25.0 Example 1 Comparative    5⁽*²⁾   20⁽*²⁾    25⁽*²⁾ (x-1) (y-1) 40 (x-1) 25.0 Example 2 Resin layer Shapes of one or more concave portions on Surface (a) Pressure sensitive adhesive sheet Maximum Mass evaluation Items height retention rate Adhesive Require- Require- Require- difference of resin layer Air escape Blister strength ment (I) ment (II) ment (III) (μm) (% by mass) property resistance (N/25 mm) Example 1 A A+ A 15.7 16.9 A A 8.6 Example 2 A A+ A 17.3 20.0 A A 12.7 Example 3 A A+ A 7.6 9.5 A A 11.7 Example 4 A A+ A 42.4 28.1 A A 7.8 Example 5 A A+ A 6.6 15.0 A A 9.4 Example 6 A A+ A 26.3 20.9 A A 10.1 Example 7 A A+ A 30.8 23.1 A A 10.8 Example 8 A A+ A 3.5 21.3 A A 12.4 Example 9 A A+ A 18.5 15.1 A A 10.2 Comparative F —⁽*³⁾ F 0 0.0 F C 18.0 Example 1 Comparative F —⁽*³⁾ F 0 17.0 F A 15.0 Example 2 (*1): This is not a measured value but is a thickness of the coating film settled in a multilayer die coated. ⁽*²⁾This is a thickness of the coating film after dried. ⁽*³⁾Since no concave portion was formed on the surface (α), the sample was no more evaluated.

TABLE 4 Coating film (y′) Flow rate of solution Fine particle (coating liquid) (g/min) Coating concentration Coating Coating Coating Coating Coating film (xβ′) Kind of in coating film film (xα′) Resin layer speed film film film Kind of coating (y′) Kind of Thickness (m/min) (xβ′) (y′) (xα′) solution liquid (% by mass) solution (μm) Example 10 3.0 27 27 27 (x-1) (y-1) 40 (x-1) 30.0 Example 11 3.0 27 21 27 (x-1) (y-1) 40 (x-1) 26.7 Example 12 3.0 27 9 27 (x-1) (y-1) 40 (x-1) 23.3 Example 13 3.0 27 51 54 (x-3) (y-5) 41 (x-3) 51.0 Example 14 3.0 27 27 27 (x-4) (y-6) 40 (x-4) 29.6 Example 15 3.0 27 27 27 (x-4) (y-7) 40 (x-4) 29.2 Example 16 3.0 27 27 27 (x-5) (y-8) 40 (x-6) 29.5 Example 17 3.0 27 51 54 (x-3) (y-5) 41 (x-3) 51.0 Example 18 5.0 (8 μm) ⁽*⁴⁾ 133 161 (x-1) (y-1) 40 (x-1) 42.0 Resin layer Shapes of one or more concave portions on surface (α) Pressure sensitive adhesive sheet Maximum Mass evaluation items height retention rate Adhesive Require- Require- Require- difference of resin layer Air escape Blister strength ment (I) ment (II) ment (III) (μM) (% by mass) property resistance (N/25 mm) Example 10 A A+ A 20.3 8.6 A A 8.8 Example 11 A A+ A 15.0 7.1 A A 10.8 Example 12 A A+ A 10.6 5.8 A A 13.3 Example 13 A A+ A 42.5 12.6 A A 23.5 Example 14 A A+ A 19.5 8.4 A A 10.3 Example 15 A A+ A 19.2 8.2 A A 11.6 Example 16 A A+ A 17.7 8.0 A A 9.8 Example 17 A A+ A 41.0 12.6 A A 24.0 Example 18 A A+ A 18.5 15.1 A A 10.2 ⁽*⁴⁾ This is a thickness of the coating film (xβ′) after dried.

From Table 3 and Table 4, it is confirmed that the pressure sensitive adhesive sheets produced in Examples 1 to 18 all had plural concave portions satisfying the above-mentioned requirements (I) to (III) on the surface (α) and these pressure sensitive adhesive sheets all had good air escape property, blister resistance and adhesive strength. In any of these pressure sensitive adhesive sheets, the concave portions existing on the surface (α) were visually confirmed.

In addition, in all the pressure sensitive adhesive sheets produced in Examples 1 to 18, it is confirmed that plural concave portions existed irregularly on the surface (α), and the positions of the plural concave portions did not have periodicity. In addition, it is confirmed that plural attached faces having irregular shapes existed on the surface (α).

Moreover, in all the pressure sensitive adhesive sheets produced in Examples 1 to 18, one or more concave portions existing in the region (Q) on the surface (α) of the resin layer had a shape extending toward any side of the square having an edge length of 1 mm, which is the boundary of the region (Q) and further extending continuously into the other region (Q′) surrounded by the square having an edge length of 1 mm, which is adjacent to the region (Q).

These matters can be confirmed, for example, from the perspective images of the surface (α) of the resin layer in FIG. 4(b) and FIG. 5(b).

FIG. 4 and FIG. 5 each include images of the pressure sensitive adhesive sheet produced in Example 1 and Example 10, respectively, taken through a scanning electron microscope; and (a) is an image of a cross section of the pressure sensitive adhesive sheet, and (b) is a perspective image of the surface (α) of the resin layer of the pressure sensitive adhesive sheet. In the image of FIG. 4(a), 10 scale marks given at the bottom right of the image indicate a length of 20.0 μm, and in the image of FIG. 4(b), 10 scale marks given at the bottom right of the image indicate a length of 1.00 mm. In the image of FIG. 5(a), 10 scale marks given at the bottom right of the image indicate a length of 200 μm, and in the image of FIG. 5(b), 10 scale marks given at the bottom right of the image indicate a length of 1.00 mm.

From the images of FIG. 4 and FIG. 5, it is known that plural concave portions exist irregularly on the surface (α) of the resin layer of the pressure sensitive adhesive sheet produced in Examples 1 and 10, and that plural attached faces each having an irregular shape exist on the surface (α).

The images of FIG. 4 and FIG. 5 show the shapes of the one or more concave portions existing on the surface (α) of the resin layer of the pressure sensitive adhesive sheet produced in Examples 1 and 10. The cross-sectional profiles of the concave portions of the pressure sensitive adhesive sheets of other Examples and the shapes of the concave portions observed from the side of the surface (α) of the resin layer thereof as well as the shapes of the attached faces of the pressure sensitive adhesive sheets were all the same as in the images shown in FIG. 4 and FIG. 5.

On the other hand, formation of any specific concave portions could not be recognized on the surface of the resin layer that the pressure sensitive adhesive sheet produced in Comparative Examples 1 and 2 has, and the air escape property of these pressure sensitive adhesive sheets was poor. In addition, the pressure sensitive adhesive sheet of Comparative Example 1 was also poor in blister resistance.

FIG. 6 includes images of the pressure sensitive adhesive sheet produced in Comparative Example 1, taken through a scanning electron microscope; and (a) of FIG. 6 is an image of a cross section of the pressure sensitive adhesive sheet, and (b) of FIG. 6 is a perspective image of the surface (α) of the resin layer of the pressure sensitive adhesive sheet. In the image of FIG. 6(a), 10 scale marks indicate a length of 20.0 μm, and in the image of FIG. 6(b), 10 scale marks indicate a length of 1.00 mm.

As shown in FIG. 6, formation of concave portions was not seen on the surface (α) of the resin layer of the pressure sensitive adhesive sheet produced in Comparative Example 1.

FIGS. 7, 8 and 9 each are a binarized image obtained by image processing (image binarization), for which the surface (α) of the resin layer of the pressure sensitive adhesive sheet produced in any of Example 1, Example 10 and Comparative Example 1, respectively, is attached to a smooth surface of a light transmissive adherend having a smooth surface, the surface (α) is observed from the side of the light transmissive adherend to take a digital image thereof, and a region surrounded by an arbitrarily selected square having an edge length of 2 mm on the digital image is image-processed (image-binarized).

In the images of FIGS. 7 to 9, the outer frame shows a square having an edge length of 2 mm. In the binarized images of FIG. 7 to FIG. 9, the white parts indicate the attached portions and the black parts indicate non-attached portions.

In the pressure sensitive adhesive sheet of Comparative Example 10, any concave portions were not formed on the surface (α) of the resin layer, and accordingly, the whole area of the surface (α) is an attached portion, therefore presenting the binarized image of FIG. 9.

INDUSTRIAL APPLICABILITY

One embodiment of the pressure sensitive adhesive sheet of the present invention is useful as a pressure sensitive adhesive sheet having a large adhesive area that is used for identification or decoration, for masking in coating, and for surface protection for metal plates, etc.

REFERENCE SIGN LIST

-   1 a, 1 b, 2 a, 2 b Pressure-Sensitive Adhesive Sheet -   11 Substrate -   12 Resin Layer -   12 a Surface (α) -   12 b Surface (β) -   (X) Resin Part (X) -   (Y) Particle Part (Y) -   (Xβ) Layer (Xβ) mainly containing the resin part (X) -   (Xα) Layer (Xα) mainly containing the resin part (X) -   (Y1) Layer (Y1) containing the particle part (Y) -   13, 130, 131, 132 Concave portions -   13 a Cross Line -   14, 14 a Release Material -   50, 501, 502, 503, 504 Square having an edge length of 1 mm 

1: A pressure sensitive adhesive sheet comprising a resin layer on a substrate or a release material, wherein at least a surface α of the resin layer is opposite to the side thereof on which the substrate or the release material is provided having pressure sensitive adhesiveness, wherein one or more concave portions formed not by transferring an emboss pattern exist on the surface α. 2: The pressure sensitive adhesive sheet according to claim 1, wherein a shape of the one or more concave portions is an irregular shape. 3: The pressure sensitive adhesive sheet according to claim 1, wherein the one or more concave portions are formed through self-formation of the resin layer. 4: The pressure sensitive adhesive sheet according to claim 1, wherein the plural concave portions exist on the surface α. 5: The pressure sensitive adhesive sheet according to claim 4, wherein positions of the plural concave portions have no periodicity. 6: The pressure sensitive adhesive sheet according to claim 4, wherein the plural concave portions exist irregularly on the surface α. 7: The pressure sensitive adhesive sheet according to claim 1, wherein shapes of one or more attached faces on the surface α of the resin layer are irregular shapes.
 8. (canceled) 9: The pressure sensitive adhesive sheet according to claim 1, wherein the resin layer comprises a resin part X comprising a resin as a main component and a particle part Y consisting of fine particles. 10: The pressure sensitive adhesive sheet according to claim 1, wherein the resin layer is formed of a multilayer structure having a fine particles-containing layer that comprises fine particles. 11: The pressure sensitive adhesive sheet according to claim 1, wherein the resin layer has a multilayer structure of, as laminated in this order from the side on which the substrate or the release material is provided, a layer Xβ mainly comprising a resin part X, a layer Y1 comprising a particle part Y, and a layer Xα mainly comprising a resin part X. 12: The pressure sensitive adhesive sheet according to claim 11, wherein: the layer Xβ is a layer formed by a composition comprising the resin as a main component, the layer Y1 is a layer formed by a composition comprising the fine particles, and the layer Xα is a layer formed by a composition comprising the resin as a main component. 13: A viscoelastic layer having, on at least one surface thereof, one or more concave portions formed not by transferring an emboss pattern. 14: A method for producing a pressure sensitive adhesive sheet according to claim 1, which comprises: (1): forming a coating film x′ formed by a composition x comprising the resin as a main component, and a coating film y′ formed by a composition y comprising the fine particles; and (2): drying the coating film x′ and the coating film y′ formed in (1) simultaneously. 15: A method for producing a pressure sensitive adhesive sheet according to claim 12, which comprises: (1A): forming, on a substrate or a release material, a coating film xβ′ formed by the composition xβ comprising the resin as a main component, a coating film y′ formed by the composition y comprising the fine particles and a coating film xα′ formed by the composition xα comprising the resin as a main component, by laminating in this order; and (2A): drying the coating film xβ, the coating film y′ and the coating film xα′ formed in (1A), simultaneously. 16: A method for producing a pressure sensitive adhesive sheet according to claim 12, which comprises: (1B): forming, on a layer Xβ mainly comprising a resin part X that is provided on a substrate or a release material, a coating film y′ formed by the composition (y) comprising the fine particles and a coating film xα′ formed by the composition xα comprising the resin as a main component, by laminating in this order; and (2B): drying the coating film y′ and the coating film xα′ formed in (1B) simultaneously. 